Thanks to the person who shared the tip about refreshing ragged drywall
edges where they butt up to a molded tub surround, using the 1/2" by 1-1/4"
or so, perforated plastic drywall edging/corner. One Lowes had the edging
for $1.55. The other Lowes nearby did not have it. I cut the flaking,
peeling edge back a little, installed the edging through the fiberglass
flange and/or studs with screws, leaving a caulking gap after mudding and
finishing. It sure took care of an ugly situation.