More games like this?

[Mehujäbä]

Really enjoyed this game and now I want to play something similar. So any recommendations on games that have:
1. Somewhat unique puzzle mechanics (that make you feel smart once you succeed lol).
2. Cozy world/graphics and relaxing sound design.
3. Story that has some depth to it.

[YAMO]

Outer Wilds

[Swamp Fox]

Return of the Obra Dinn is totally unique. Great music too. Outer Wilds too.

[lortonix]

Heaven's Vault is a somewhat similar game, with a glyph-based language to decipher, beautiful cartoon landscapes and an interesting story/world to discover. Highly recommended!

[Esper-ame]

Gorogoa has unique puzzles but is very short. Artistic and cozy.

[J4MESOX4D]

As already mentioned
https://store.steampowered.com/app/653530/Return_of_the_Obra_Dinn/

[Sigma957]

Does this reference the Anunnaki?

[Vitlöksbjörn]

If you're looking for something less known, I suggest Mu Cartographer:
https://store.steampowered.com/app/513360
It has a unique story, strange mechanics... but I think it's kinda hard, so it might make you feel stupid instead.

[Ted Bunny]

I learn languages for fun. It'd be really cool if one of these games had a full conlang with actual grammar and a phonetic alphabet. I think the market would be too small, unfortunately.

[SnuggleBombs]

Any of the Myst games fit the bill

https://store.steampowered.com/bundle/37135/Myst_30th_Anniversary_Collection/

[Ruth E.]

Case of the Golden Idol and its sequel that just came out feature similar fill-in-the-blank style puzzles that are quite challenging, with stories full of twists and turns.

[dandelion_sprinkles]

Check out 'The Witness'. It's another puzzle game that involves exploring an island with a hidden game mechanic that only adds to the experience. Once you notice, you can't unsee it. This game is different from the Chants of Sennaar in that you aren't learning languages, but gives me the same level of "AHA" moments of accomplishment. The puzzles seem simple but it drastically evolves into taking into consideration your surroundings to solve puzzles.

[bethhas1]

Journey is a fantastic game that is a bit less puzzle focused, but gave me very similar vibes in terms of story and atmosphere.

[ben2613]

Recently I find International Linguistic Olympiad exists and the problems are hard enough to struggle for hours.
You can find all the past contests here
https://ioling.org/past_contests/

[Sh0dan451]

Heaven's Vault has already been mentioned... so I can die happy.

[misnia]

I would add Fez to the list.