If you enjoy city builder games you might wanna try Songs of Syx out. You basically build an empire containing potentially thousands of citizens. There’s no way I could possibly do the game justice in a comment, so you might wanna check out a let’s play or the Steam page

Narita Boy is a really cool glitch aesthetic sidescroller

Owlboy was better than I expected it to be.

Does Tunic count?

Best to jump in without spoilers, but it's way more than a Zelda/Souls like. So. Many. Layers.

And at a similar depth, but from many years ago. The Ur-Quan masters (space game) https://sc2.sourceforge.net/

Kenshi - a brutal, and sometimes janky squad free roaming game. I have far too many hours in that.
Pulsar - Lost Colony - Fun game if you have a few friends around. Pretend to be Captain Kirk - except chaos.
Rimworld -- Dwarf Fortress lite
Dwarf Fortress - Grand daddy inspiration for most other games
Torchlight - Diablo
Project Zomboid - All your top down zombie hunting dreams come true
Carrier Command - Drone carrier warfare
Nebulous Fleet Command - The Expanse.

Does X4 count as Indie?

Superflight

Really engaging game with a short, easy to understand mechanic. It's fun just to put on and fly around for a bit every now and then.

Lost Pig And Place Under Ground

An old-fashioned text adventure, one of the best ones I've played.

Pig lost! Boss say that it Grunk fault. Say Grunk forget about closing gate. Maybe boss right. Grunk not remember forgetting, but maybe Grunk just forget. Boss say Grunk go find pig, bring it back. Him say, if Grunk not bring back pig, not bring back Grunk either. Grunk like working at pig farm, so now Grunk need find pig.

Check it out

Here are some games I have not seen mentioned yet:

Valdis Story: Abyssal City
A 2D metroidvania, with the best combat in the genre. It has infinite combos, parrys, skill cancels, a magic system, and 4 characters that play fundamentally different. You get scores for the bosses, which really motivates me to learn the combat well beyond just finding one thing that works well. If you have any interest in sidescrollers, then this game is for you. Controller is required thou.

Zero Sievert
Ever wish that tarkov had a singleplayer mode? Well look no further, Zero Sievert is a top down extraction shooter, that is still in early access. But whats already on offer is really solid and a lot of fun. It has that tense atmosphere when you find something good and want to extract, without wasting massive amounts of your time.

Ollie Ollie World
A 2d skateboarding game with a unique control scheme, that has a very high skill ceiling. Its score chase, with online leaderboards, daily challanges, seasons, and so on. I like its music and artstyle a lot, bit if thats not for you, you can check out the older entries in the series, that look not as 'out there'.

Hyper Light Drifter is a really pretty game with tight controls, fair difficulty, excellent music, and some of the best atmosphere of any game I've played.

Ctrl Alt Ego

It's like a System Shock or Prey 2017 that has even less emphasis on "conventional" combat and more general problem solving. In some ways I feel like it's what you get if you grow an "immersive sim" out of a "puzzle" game like Portal instead of out an FPS or RPG.

Ooh, I love finding obscure indies. There are an awful lot of games on Steam and Itch and other platforms that are amazing experiences, but that almost no one has ever played or even heard of for one reason or another.

One of my recent favourite zero-budget indies is Sally Can't Sleep, a strange first person platformer with a lot of focus on fun, versatile, and exploitable movement mechanics. The dev sacrificed visual polish for quantity and style, so the game has a lot of interconnected levels with a big variety of different mechanics and visual styles - it's a really good example of how much a solo developer can accomplish.

Another one is Worlds, which is a 3D stealth-shooter-platformer-adventure? I like it for the same reason as Sally Can't Sleep, it's ambitious and creative, and you can really feel the developer pushing against their limitations to release something that punches far above its own weight.

Also, both these games are very cheap, even at full price!

Firewatch - recommend you wait for a sale but its a great story game that is on steam and gog and even native Linux

tabletop simulator - tons of card and board games that you can play with your friends if it exists it might be ported has native Linux

golf with your friends - great mini golf game to play with your friends similar to tower unite golf but better has native port

american/europe truck simulator - trucking game that real truckers say is the most realistic trucking game and they try to help with all issues and is even native Linux

https://store.steampowered.com/app/1641020/my_brother_lives_in_a_canyon - my brother lives in a canyon - great story game that is made by one person and it does not take long

Bloons tower defence 6 - tower defence game where you pop the bloons to defend your base

eastward: topdown-zelda like. gameplay wise, though it's quite easy. the story is charming, with all the quirkiness from earthbound, although the main plot is actually more akin to the last of us 1, for some reason, or at least it kinda felt like that to me. the visuals are absolutely gorgeous, as is the soundtrack.

phoenotopia awakening: an action rpg-metroidvania mishmash, and a surprisingly large one at that. if you're into challenging and backtrack heavy games, this one does the job very well.

crosscode: this one's been mentioned a bunch on this thread, and there's also been a post here about it a day or two ago, but i'll still mention it because it's just that good. another topdown-zelda like, but keep in mind that i've seen it described as a puzzle game masquerading as an rpg, which may be a more apt description.

Cassette Beasts! It's a monster collecting game. It adds a lot to the genre (definitely not a clone) and the music is awesome. It got amazing reviews so I'm not sure how hidden it actually is, but I really enjoyed it!

It's admittedly gotten a lot of shout outs with Diablo's release, but Grim Dawn. Just a super great old school ARPG with a fun multi class system. I think I made a mistake by letting it be one of the first in the genre I really got into, so it's kinda tough to find another one that competes.

If you like RW/DF, look into Factorio, Satisfactory, Oxygen Not Included. They're all sim/logistics games with different focuses. Factorio is more logistics/big factory minded. Satisfactory has more exploration. Oxygen Not Included is very physics based, you'll need to understand heat transfer by mid game.

I like Deep Rock Galactic a lot more than I thought I would. I don't usually like FPS's. It's coop only. There's mining, and the terrain is 100% destructible. The movement powers are amazing! I love the platform gun. Also, playing dress up with my chunky, ugly dwarf is the BEST.

Hardspace Shipbreaker is amazing. It's shorter than I want, but it's SO well done. I want more of it! You play a disassembler, taking ships apart and chucking the parts into their respective bins. However, the dystopian management has zero worker safety, so it's not so simple. The music is amazing. The voice acting, superb.

Super Kiwi 64

Retro 3D platformer in the vein of Banjo Kazooie.-

Fear and hunger is the most intense RPG-style horror game I have ever played. It's vile. It's fucked up. And it's honestly enthralling. Pay attention to the content warnings on the steam/itch page if you look it up, they're serious. It's like a game in the Berserk universe, but you're NOT Guts.

Super Auto Pets has replaced Hearthstone for me, it's fantastic.