Crazies - an urban tribe of autistics, ADHDers, bipolar and other neurodiverse people. They form their own neighborhoods or just form roaming gangs. Whatever POD that makes there a dedicated otaku ghetto in the united states just like Akibahara - maybe in the future this happens in say San Francisco or Seattle or Portland, or more likely in Vancouver. (all those cities have large numbers of vagrants, many of them from mental facilities that closed down and they moved there due to the relatively nice climate).
Neo-Techies. Distinct from hipsters, they walk around in public in cyberpunk garb and act like they are living in the world of
Blade Runner.
Not so alternate, but modified: Moped Gangs. Originally formed by moped connoiseurs, they spread into legit gangs in cities like Chicago and NEw York. Get into conflicts with motorcycle gangs, as well as bicycle gangs (yes there are bicycle gangs). Their main turfs are the highly developed inner city regions, and relatively rarely the suburbs. The idea is influenced by the anime series Durarara and the comic Moped Army, as well as The Warriors i'd say.
also modified: Otaku gangs/weeaboo gangs who go out looking straight out of a shoujo or lolicon anime, or maybe a shounen anime - they incorporate east asian culture - as well as their 'original' culture (e.g. black otaku gangs incorporate Swahili and Ebonics sayings, as well as olld black folk tales into their garb and "feel" - Irish gangs incorporate Irish mythology like the Dullahan as well as other things, etc etc).
I'm tempted to say there could be a separate hikikiomori gang from ex-hikkiomori who networked with fellow hikikiomori in the same city and did not fit into the 'more social' gangs.
I am bumping this too. also related thread
https://www.alternatehistory.com/discussion/showthread.php?p=4592914#post4592914