If you got Spotify on desktop you could just select all your liked songs and drag them onto some other playlist.

Should work multiple times, just click „don’t add“ when it asks you if you want to add duplicate tracks.

I tested and created a IFTTT recipe for this: https://ifttt.com/applets/iMnNGt3V-backup-spotify-likes

Despite the incorrect labelling "Saving a spotify track" means liking it, not "downloading to your device". So you can add it to another Spotify playlist.

To get historical likes, cmd-a / ctrl-a (or equivalent) all Liked Songs tracks and drag them into the backup playlist.

I think you could use soundiiz.com for that.

Soundiiz is great. Only way I was able to get my playlists exported as CSVs