If you haven't played them the original Fallout 1 and 2 (the Fallout 2 Restoration Project is a big recommend) and Arcanum are classics as well.

Planescape: Torment is a classic from that era

Check out all the old "immersive sims" like Deus Ex, Arx Fatalis, System Shock 2, and Thief.

If you're cool with emulators, PSX has a metric ton of JRPGs that will absolutely devour your life.

Morrowind is still a lot of fun for some some of that classic Bethesda goodness and runs great in OpenMW

You could look into Spiderweb Software games. It’s a veteran mom and pop indie studio from before indie studios were a thing. They’re still going strong in their retro RPG niche and I’m pretty sure their games run on a potato. Recently I’ve enjoyed Queen’s Wish 1 (2 is in my backlog). I have fond memories of the Avernum series as well.

Caesar 3 is a fantastic city builder that will run on just about anything. https://store.steampowered.com/app/517790/Caesar_3/

A few of my favourites:

• Darklands (1992) - one of the OG RTwP games. Fairly low-fantasy, you play a mercenary gang, doing mercenary things. It's quite old, and like lots of games of its era, is very obtuse, and not a lot of information is available in game, but if you can get past that, it's a great game.

• The Elder Scrolls II: Daggerfall (originally 1996, but I recommend the Unity fan-rewrite Daggerfall Unity) - Procedurally generated dungeons and wilderness, an absurdly huge world, much deeper skills and stats than later entries in the series. It's not my favourite in the series (that goes to Morrowind) but Daggerfall is certainly definitely worth playing, and the Unity re-write (with mods!) makes running the game a breeze.

• Ark Fatalis (2002) - underground first-person RPG, with a very unique magic system, incredibly immersive environments (one of the least "game-y" worlds I've experienced in a game), and a branching story affected by your choices. It was open-sourced a few years back, and a community has formed around a continuation of it, known as Arx Libertatis.

• Gothic (2001) and Gothic II (2005) - third person RPGs made in and very popular in Germany. Another pair of incredibly immersive RPGs, way ahead of their time in many aspects. The towns and cities all feel very lived in, and the NPCs themselves feel more alive than even some modern games (looking at you Cyberpunk). The character progression is absolutely fantastic, as is the way of levelling up skills and stats. Much more immersive than just "watch number to up". As with Arx, there is some plenty of that early 2000s jank, and extremely wonky KB+M controls, but there are mods on that add controller support, and various other modernization/QoL features as well.

• Star Wars: Knights of the Old Republic I (2003) and II (2005) - Star Wars RPG taking place thousands of years before any other established stories. Very open ended in both story and character progression. It's like a Baldur's Gate in 3D, but Star Wars. The first is fantastic on its own, but the second needs the Restored Content Mod.

• Divine Divinity (2002) - from the people who would eventually make Divinity: Original Sin. Diablo-style combat, loot, and inventory management, with classic-cRPG-style questing, story, and character progression. There's also a follow up, Beyond Divinity, that I haven't personally played yet, but I imagine is more of the same goodness.

I was a huge fan of Wizardy 8 when it released. Being able to type questions and responses to NPCs in a 3D RPG was mind blowing to teenage me. The older Elder Scrolls games like Daggerfall can be fun for a while as well.

The isometric games from Black Isle Studios were also top notch 90s/2000s RPGs. Baldur's Gate (I & II), Icewind Dale, and Planescape: Torment are all fantastic. Planescape is less combat focused than the others.

Fallout 1 and 2, and Grim Dawn are all excellent choices, although Grim Dawn is newer.

I highly recommend looking into Spiderweb Software games. They've been pumping out top down turn based tactics rpgs for years now. I am not sure of the viability on Linux, but I'm sure there is a workaround if anything.

The Avernum series in particular is great if you're into detailed character building, exploring, and high difficulty optional quests/bosses!

Septerra Core. I used to go to a friend's house and we would take turns playing. It's been.. a long time, but I remember loving it.

Have you played the old LucasArts SCUMM adventure games? Full Throttle, Monkey Island, The Dig, and Grim Fandango are masterpieces.

Dungeon Siege (2002) is a nice RPG; 3D, isometric-style default camera, slightly tactical order-based movement/attack, and a fully streamed world - so no loading screens during gameplay.

It certainly has its fair share of jank as well, but it does well otherwise.

Baldur's Gate I and II, Dungeon Keeper, Dune 2000

OP wanted PC games, but here is an old Amiga classic ported to multiple platforms: https://github.com/Pyrdacor/Ambermoon.net

Interestingly enough, I would say breath of the wild. I thought it was only okay. I didn't love the powers, the world felt big but empty, idk just didn't fully click with me.

I feel like totk has everything I was missing in botw. Could be because I didn't really watch any promotional materials and had lower expectations, but totk blew me away.