The idea that the GM needs to be this epic narrator as if they were an author is something I wish would die. The medium of play is different.

Here's some things I do for long travel scenes that have no backing mechanics:

• ask the PCs pointed questions. "You don't see any animals in these vast plains, how do you eat?" or "The road is alternatingly rocky and muddy, and it does a number on the wagon's wheels. How do you keep them in working order?" or even "The night out here is too dark. What do you do to make each other feel safe at night?"
• when pointing anything out, give two details and a small twist. Encourage them to ask questions for details, but don't drill down into nitty gritty scenes. "The motion you thought was a river from a few miles back is a mass migration of centipedes. They seem too small to be of harm, and Karlen your guide demonstrates this by striding across them. The ones he crushes underfoot give off a sweet maple scent"
• ask players individually how they pass the time. Do they zone out? Practice the florghorn? Play betting games with the cooks? Whatever they say, drill in and ask more questions.

What I'm trying to get at is that the conversation, not narration makes travel memorable. Converse with your players. Encourage them to converse with you.

Most of the time for travel, i usually default to "red lining" (which is a concept that unfortunately shares its name with a practice of racially profiling people for housing purposes, but is not related in any way), which is a quick blurb/explanation talking about the travel. The idea is supposed to be similar to, like, action movies such as indana jones where you'd see a map and a "red line" is drawn showing their travel as a quick transition to the new locale.

I also prompt players for anything they want to "do" during their travels, which can be whatever the players want to call out.

That said, i usually try to include in my description just quick descriptions of time frames, and sights the characters would see. I.E. "You travel through the foothills for around a week, on the way you take note of the lush forests, rolling terrain, and the peak of mount doom far in the distance looming ominously. You finally arrive at the hamet of (city)."

I like point crawls for this. I mark a few points of interest and how long it takes to get there. Travel is fairly abstract until they get to a point of interest. Once they get to the point of interest, things slow down so that they can find cool things, meet npcs, fight monsters or some combination of those things

If the area is hard to navigate then a failed survival check might send them to a different point of interest

I usually try to drop in one scene or situation along the way usually at the site of a notable landmark. You can roll randomly for the landmark and maybe two groups. Maybe they’re fighting. Maybe one group already beat the other group. Maybe they’re friendly. Just a situation to expose something about the world and it’s history and people.

You can also use it as an opportunity for campfire tales. Ask each player ahead of time to think about what their character thinks of what they’ve done so far and where they’re going. Have each player share their thoughts during a long rest along the journey.

Finally, if the characters are traveling anywhere with risk you can define some traveling roles like who is scouting, who is trailblazing, and who is provisioning. Have them roll checks on these jobs to give you some interesting ideas about what might happen along the journey.

Sometimes I like the hurky-jerky travel. In my big campaign my players have worked their way up to level 15 and are on the way to the story's main villain for a final confrontation. I don't plan to end the game, but probably 'end' the campaign by pivoting, allowing players to retire their characters if they wish, and deciding on a new story and setting in the same world. As they progressed it became harder to justify a challenging encounter on the road, especially after level 10 or higher and on paths they've already been on and where you wouldn't expect to encounter a powerful foe. If they're traveling between their current location and somewhere they have been before, I'm fine with treating it like a videogame fast travel, my players want to go to a different place to advance the story, not to deal with random encounters between here and there.

For lower level parties and for travel to places the party has not yet been or on a path they have not yet taken, I do a few things.

First, the party will decide how they're going to get to the new location: do they set out on foot, or hire a carriage or even take a ship? (in my now-high-level campaign, the setting is a town and surrounding area at the edge of the continent, lots of ships available and the party has actually acquired a couple ships of their own) We often roleplay the party deciding their method of travel, and finding what or who they need to accomplish it, so if they're hiring a carriage they will find the carriage company or a local citizen with a carriage large enough to accommodate the party. Once the mode of transport is arranged I'll figure out an appropriate amount of downtime and ask each player if they have something they want to do/work on while on the road. The amount of downtime will depend on the distance they're going and method of travel they're using. There's plenty of good downtime activities, some of my players with magic user characters will use the time to make scrolls, or copy from a scroll they found into their spellbook. If they're traveling on foot or horseback there is obviously less downtime available to them to make progress on these activities since the bulk of their day is dedicated to the traveling, so my party likes to hire carriages or use a ship.

Once all of that is arranged I let them roleplay some conversation. If they hire someone to transport them they'll often want to speak with that NPC at length to learn more about the area and what local lore they can. I also often use the actual travel as an opportunity to introduce a new character who is passing through, or let them cross paths with someone they've met before and give them an opportunity to catch up or learn the local news for the area they're going to.

I used to do random combat encounters in the middle of travel sequences, and I still do in my spin-off campaign where the players are all goblins and kobolds because it's a great opportunity for mischief and hijinks, but I try to not do that in story driven campaigns. An unexpected combat encounter in a travel sequence is jarring, slows the story down, and is just keeping the players and me from the game content we really want to be exploring.

First decide how gamey and mechanic you want it. A tried and tested but fairly prep intensive way is a hexcrawl. Rolling tons of random dice for every travel day can also be a neat way to fill a session! Roll for weather, environment, maybe a big list of random encounters, geographical features, local fauna etc pp. The dice will surprise even you, be ready to improv.

More free form ways would be to make the travel a skillchallenge/extended challenge, or use a montage approach as presented in fellowship or 13th age.

I like to mix and match the last 3 things I mentioned: random rolls, skill challenge and montage. Of course, this heavily depends on gam, too!

So I use a generator that I've built filled with prompts collected from books and community posts. I've got all of these broken down into categories. Theres a few for combat at varying levels of difficulty, and those include some where the combat is already over, and the parry can talk to the winners or aid the losers, or about to start and the party could possibly intervene to prevent it.

Other prompts include foliage, beautiful sights, landmarks, historical events, npcs, whatever your players are likely to be interested in. You got a druid? Plants and animals. Bards or other social characters? You need travelers to meet. It's all about knowing what hooks your party will bite on.

So let's say you have a list of 8 things that are happening between the two points of travel. You need a meaningful way for the party to choose what they want to interact with. You could draw a small hexmap of the area and put a reference for each interaction on it asking them to move a token as they decide to travel. Or you can consolidate to a few paths and group your prompts along each one. Here's an example:

"You stand at the top of a high hill and survey the area ahead of you. There appear to to be two paths forward, the one on the left has recent wheel tracks from a wagon that looks like it was weighed down with cargo (this signals that merchants or refugees came through here), it leads into a forest with a dense canopy that covers the valley ahead. It looks like there is a clearly as the earth slopes up the far side (maybe there's a lake, or a small village, just a cabin, the site of an ancient battle or a hill dwarf logging operation.

The other path heads towards the mountains, it looks like it's going to involve some climbing (now the parry knows there are skill challenges this way), you can see some sort of altar or shrine on one of the lower cliffs that glitters with precious metals (do they seek treasure, is there a cleric or paladin in the party?). There are footprints here, but they are faded, no one has gone this way in a while (this means I've grouped the harder combat encounters here too)".

The key here is not just asking them to choose arbitrarily, but to inform them of what's coming and give them a chance to chose what they want to do. Both paths will lead to the same place but have very different experiences on the road.

I've gotten pretty wordy already so I'll stop here, but if you want to go into more detail about building roadside encounters, I'd love to.

I started my current campaign with absolutely no plot in mind. I chose characters and players I liked and gave them a campaign long escort quest of an author that needed to travel and see remote places and customs to write about. So these kinds of encounters are a huge party of my game.

Describe the place they are leaving. Ask them how do they feel about that. Then do a montage of their journeys (just a couple scenes) and ask someone to pitch in, like «Ranger, what's totally unexpected grows here?», or «You see a small pillar of smoke, seems like there is a small village off the beaten path; Cleric, who do they praise here?». And after that you can tell them «...so, you're here».

Maybe have kind of a group based skill challenge for the whole thing?
Like instead of going through the minute detail of everything, summarize the whole thing into a few skill checks, but without bogging down with a million checks. Ask them which skills they wanna contribute to the journey?
Relevant Matt Colville vid:
https://www.youtube.com/watch?v=GvOeqDpkBm8&t=567

Idk, maund they each commit a few specific skills and how that goes kinda becomes the basis of the narration even though the thing itself is mostly uneventful.

Maybe they'll end up finding a shortcut, maybe they have a particularly bountiful hunt/meal, or maybe clear an obstacle, maybe the bard's performance has them in particularly good spirits and they make better progress. Successes vs failures wouldn't mean the travel fails, but might help flesh out how that happens or even just influence the time they take to get there.

Just a few rolls for the whole thing.
This could keep it more dynamic than just fast forwarding, without having to go through every day/ night cycle and spending half a session inbetween every place.

On avoiding clearly indicating to the players that something is happening, maybe have "non-encounter" events here and there?
Like, if travel is always a "cinematic" and whenever they're in control, it's something special, then they'll always expect something special.
Interrupt whatever they're doing with something more mundane, fluff.
Even just a particularly nice sunset.
Maybe they find a landmark that's just that: a landmark that they add to their map but that has no ulterior purpose.
Or maybe a tree that was struck by lightning obstructing the road or whatever road hazard (but NOT an ambush for a change). Do they just avoid it? Clear the road?
There's probably not that many road maintenance crews going around, whatever obstacle will probably still be there when they come back. Or maybe an NPC has to deal with it.

Disclaimer: I haven't DM'd anything yet, but coming with some interesting narration for everything isn't something that would come easy.
Shifting some of that responsibility to the players and which skills they choose to commit for the journey can kinda tell a story in itself or at least jog some of that creative bone in action with how well/bad they're doing.