Update:

Direct wire (no ballast) LED T8s were on sale half price, for $15 I got two..

Rewiring was a 5 minute job because the T12s were Rapid Start so the tombstones already had unshunted contacts. (I didn't know that until I took them apart and looked, and checked each one with a meter, so it took longer than 5 minutes, but it COULD have been a 5 minute job).

The new lights look fine and they are much quieter, no annoying buzz.

How long they will last is another story, I'm skeptical, but they claim a 5 year warranty.