If it’s cement based I would start manually- hammer and a five and one tool or similar small chisel to forcibly separate the self leveling material from the tile. If it’s a glue that’s petroleum based you will need to use chemicals. Any photos you can share?

Are you trying to go back to the tile floor, to make it useable again? I"m afraid I can't offer much help with that.

My experience with multi-layer floors and applied adhesives of various kinds is that it is often way easier to just pull the whole mess out, down to the joists,and lay down a new subfloor to allow you to begin fresh with a flat, level, and stable substrate.

I'd like to salvage the original tile underneath if its possible. What I've got so far looks amazing.

That looks like a petroleum based product. Remove as much as you can with brute force. Then use a wallpaper scraper and single edged razor blades to clean off the face of the tiles. You may have to use a chemical stripper for the final layer of gunk. Hard to advise without playing with it in person

I've gotten old lineolum up with boiling water.