Board Game Arena

Will there be some fan factions from bgg forum just like TM. And challenge mode of gaia on steam is so interesting, expect new game mode on bga.

There are no plans to implement the unofficial factions. I don't know that the publisher has even given permission for them.

TM fan factions are an official expansion, like fan created Encounters expansion for Scythe, not the random fan factions published on BGG. I haven't heard of any plans for such expansion for Gaia, unfortunately.