For the past few years Spotify’s Discover Weekly has been the main way I discover new (to me) music. Secondarily I guess just from browsing the related artists of the ones I already listen to. Looking for other strategies inside or outside of spotify.
In addition to some of the music sources listed here, my personal hack is to create monthly playlists where I drop literally everything (new and old) that I like. After the month is over, I check the spotify playlist suggestions to discover even more stuff related to what I’m already enjoying.
At the end of each year I just compile all monthly playlists into one, which is a fun time capsule for music I discover. Been doing this since 2015.
I do similar, it definitely makes spotify better for discovery. I read an article a while back on their algorithm and how it utilizes playlist-ed songs. I wish I was as organized as you, I pretty much go in one playlist until it gets too annoying long then “archive” it into a 1 or 2 year chunk.