So it seems 0 AD (FOSS RTS) is still alive

Looking at their website, and their revision ticker on the side, they are going full steam ahead with improvements after a long lull in development. This new alpha also includes a very important feature that finally unlocks the possibility of many custom campaigns hitting the community (just like in AOE2 Age of Kings).
0 A.D. | A free, open-source game of ancient warfare (play0ad.com)

Anyone who would rather not purchase Age of Empires 4 through the Microsoft Store should play this if you want something new. The revision log also hints that they have automated builds, and the engine it is built on is becoming quite an RTS backend for those who want to fork the source for a custom project.

For a FOSS project it is looking pretty good now, as not too many games in this category even get to this state while remaining active.