Fan projects like Fallout: New California and Fallout 4: New Vegas get plenty of attention for overhauling the recent entries in the Fallout series, but the classic, turn-based Fallout RPGs also have passionate modding communities, and one of them really, really wants Fallout 2 to be an MMO. They iterated on the idea several times before Bethesda ever explored multiplayer itself with Fallout 76.
The latest Fallout 2 MMO project is called FOnline 3, descendant of FOnline 2, FOnline Reloaded, and FOnline Aftertimes. Each are based on the FOnline system which uses resources from Fallout 2. (In an effort to avoid a copyright notice, the creators insist that you own a copy of Fallout 2 before downloading an FOnline project, which you absolutely should—it's on Steam and GOG)
Not all in the FOnline family have stood the test of time, specifically FOnline Reloaded, which modder KompreSor tells PCGN is the abandoned project that FOnline 3 is meant to replace. Although what we see in the trailer isn't turn-based like Fallout 2, KompreSor also told the site that "certain parts" will be turn-based.
FOnline 3's website provides a somewhat jumbled description of the game, saying it's about surviving in the wasteland while fighting on behalf of one of the NPC factions, and is meant to improve on FOnline Aftertimes while removing "what was unplayble."