I'm not in pretty much any fandom besides for Vocal Synths anymore (and even then i was never really "active" in a social media sense anyways). But I was a huge fan of A3! prior to the English server's closing, and the extremely small group of fans were mostly extremely kind and awesome.
Unfortunately, that game was a Gacha game with it's main appeal for me being it's also a Visual Novel with a ton of charming guys + great writing. And when I can't read any of the text because the English version completely evaporated off the face of the earth, I fell off pretty hard. The servers shutting down in late 2021 / early 2022 was one of the worst things to happen to me in terms of gaming

omi fushimi i miss you every day...
but most of my other historical hyperfixations had awful fandoms. the Fire Emblem fandom circa the Awakening / Fates era and the Pokemon fanbase in general is a hotbed of infighting that makes me keep an arms length from them, and I've had such bad experiences with the Utapri fandom I eventually just completely gave up. All things considering, the Vocal Synth fandom is vauge and wide enough you can easily find your niche and stick to that clique.