I've seen libre.fm mentioned a lot of places over the last few years. I don't know if anyone here has actually used libre.fm, but I signed up for an account 8 hours ago that I have no way to access because I never got an authentication email. Nothing in my email account, nothing in my spam. No way to resend the email on the page. All the tools I've found for importing from last.fm are years old and don't appear to have been updated in a long while. I found this guide
on reddit from 3 years ago on how to do it. No idea if that still works. I could have tried it if I'd been able to access the account I created.
As far as Listenbrainz, I've had an account with that for a while. I regularly import my last.fm scrobbles there. You click a button and they're there: dead simple. Besides accepting scrobbles (which they call "listens," because apparently scrobbles is a trademark) and feeding them back via their API
, it doesn't do much, but I'm not sure it needs to for our purposes. Listenbrainz is by Musicbrainz, which is a foundation with some backing $$ behind it.