Take a look at Musicroamer
you type in a favorite artist and it uses the spotify recommendation stuff to find similar artists
if you find one that sounds nice then you can then create a branch of artist that are similar to them
(probably a horrible explanation, just mess about with it for a minute and you'll get an idea how it works)

I've personally used it to find quite a few new favorites since ditching Spotify in favor of a self hosted Navidrome server

as for FLAC downloads check out Qobuz, which has unlimited DL plans
alternatively if you would rather sail the seas, search up Firehawk52 for a guide

https://www.qobuz.com

you can purchase individual albums through the download store.
or you can buy a month of the unlimited download subscription and download everything you want
can be downloaded in either MP3 or lossless FLAC (though, don't download above CD quality because you won't hear the difference)

there also may or may not be a set of resources out there under the name Firehawk52