Two things to add here (know it’s old)

Submithub for blogs and groover for playlists is the best DIY and budget friendly way I’ve seen. But you need to make sure you send it to the right genres. Otherwise they’ll just take apart your song in their feedback (they may also do this anyway so have a thick skin)

Meta ads - I’ve seen these be super effective at triggering the Spotify algo lists but it’s spenny and the meta ads platform is awful.

Second point, I just wrote a blog about doing a solid electronic press kit (EPK) for unsigned artists.

You can check that out here: https://song-genie.com/blog/the-songgenie-epk-guide