They all use the same extension core

https://git.mihon.dev/

A bit longer than that. Kakao went after tachiyomi for a number of extensions, the biggest ones being mangadex and bato.to. the Tachiyomi team took the plugins down without fighting back. A day later they announced they’re taking down the plugin repo effective immediately, likely out of fear of future action but it also could’ve been discussed behind closed doors with the Kakao team - we don’t know. Now Kakao is trying to sue the entire app, all of its developers and anyone who’s forked it on GitHub for infringing copyright.