I recently became aware of Athena Crisis. It is as they say "a modern retro turn-based strategy game". It is clearly inspired by Advance Wars and runs on a lot of systems because the codebase is on JavaScript, React & CSS. Downside is that it's only online play at the moment. But well, this means it runs natively on Linux and I have to say it works just fine. It is far from completed as they just entered early access on Steam a while ago.
I tested it on Steam Deck where it runs okayish. Clearly it hasn't been optimized for controller play yet as you need to use the mouse for some interactions.

General info about the game: https://athenacrisis.com/
Their article on entering open source (MIT): https://cpojer.net/posts/athena-crisis-open-source

More niche info: there is a speedrun challenge going on for the next couple of days. That's how I became aware of it anyways.
https://www.speedrun.com/challenges/ml3l8pr0-Athena_Crisis-athena-crisis-completionist-speedrun-challenge

BR happycamper

PS: Hi btw! This is my 1st post as I just had to recreate my account bc I couldn't find my old credentials