Komga is always mentioned as a good option for this. I use it for books, manga, and comics, but my requirements are quite minimal (koreader sync, opds, and mihon), so it might not work for you exactly.

I do metadata fetching using komf, documentation is a bit lacking but once setup is pretty good (I use it for both manga and comics) and it does everything automatically. There is also a browser extension that provides a UI for it. For comics sometimes I use ComicTagger for manually reviewing tags too. I would just read carefully the folder structure Komga expects if you go with that, to avoid having weird surprises :)