I think your best bet might be the Internet Speculative Fiction Database, which has mountains of bibliographical entries for obscure and forgotten sff authors. The SF Encyclopedia is another good source, but that's more focused on SF in general rather than solely authors. There's also the SFE's sister work The Encyclopedia of Fantasy; it hasn't been seriously updated since the turn of the millennium, but if you're looking for an old fantasy author, you might get lucky.
the peril of reading old scifi/fantasy is i’m left trying to navigate author websites that were clearly hand coded in html 20 years ago and haven’t been updated since when i just want a nice neat list of all their books that they somehow don’t seem to have 😭