ouch. Someone's gotta have a good idea what to do

It looks like a very clean break. It might look fine if you just glue the paint back flap back down. Use a syringe to squirt a bit of glue directly under the flap. Don't use too much as it will flow up and out of the crack.

Agreed, a water thin glue applied with a syringe should work nicely. As you apply weight, some glue will undoubtedly bubble to the edge, have a paper towel ready to wick away the excess, do not wipe it or you will get residue stuck everywhere and you will need to use a 2000 grit sandpaper to smooth it out.

I would do a little glue underneath and then once it dries I'd put a square of mylar over it.

Obvious but strongly recommend making sure you have a clear path and correct size clamp to compress this repair after glueing! Wax paper and a good block to be certain your repair is the least obvious as you only get one chance to fix this. Large low cost C-Clamps are available from Harbor Freight. Good Luck!!

vid1900 describes this at https://pinside.com/pinball/forum/topic/vids-guide-to-ultimate-playfield-restoration#post-551406