Two more games with in-game achievements:
THE KING OF FIGHTERS '98 ULTIMATE MATCH FINAL EDITION
THE KING OF FIGHTERS 2002 UNLIMITED MATCH

Thanks Alexim!

The new Avernum remakes have ingame "Medals" for various things.

Can you upload a screenshot? Do they get wiped if you start a new game?

Due to the nature of the save system in use, all achievements are persistent though all save slots.

Edit: https://imgur.com/a/T0qLYqc The attach button didn't feel like working.

Excellent, thanks! Can you list the Avernum games that have the medals system? Is it in all of them?

The ones with the subtitles, and none further. So Avernum: Escape from the Pit, Crystal Souls, and Ruined World.

Added, thanks again!

Do the books of Eschalon count? They have several conducts/challenges you can ascribe to, which can be failed under strict conditions.

I don't know how they work, but my policy in cases like these is "could you make a list of GOG Galaxy achievements out of them?", if the answer is "yes" then yeah, they count :D

You can see here, how they work.

They look cool, I suspect they're not save-dependent, are they?

Er, I'm a little rusty on the details, but I think it is actually per character.

They actually sound like the "challenges/feats/achievements" of Indiana Jones and the Fate of Atlantis, which are off the list because they're pretty weird and are not what most people consider achievements to be in the modern age. I'll look into it as soon as I can, thanks for bringing it up!

No, Indiana Jones was left of the list because it only gives a certain score for things you have to do while playing the game (much like the old Sierra games did). Achievements have nothing to do with the fact where they are shown, Iif they only show on Galaxy or Steam does not matter - there are many games which store their achievements in a list inside the game. Most people define achievements as additional tasks that are not required to finish the game but are optional challenges leading to additional playtime and/or replayability. Yes, I know that some games also show achievement that cannot be missed because they are part of progressing in the game but I never saw a user beingt happy to unlock such a kind of achievement.