I personally love Naev and Mindustry
Battle for Wesnoth - a turn based tactics game in a fantasy setting. It’s also available on Steam and itch.io. Coincidentally, version 1.18.0 was released yesterday.
I wish that the original use-case for Battle of Wesnoth’s engine, Wargus, was still being actively developed
Wargus and Wesnoth both run on the Stratagus engine, which was originally developed as a reimplimentation of Warcraft 2 . The engine split to allow for new games to be made, and the War2 functionality was shunted into Wargus where the project remains to this day