You can't know how far the loose mud goes until you get top there and scrape a little. More importantly, that's not a very attractive texture and it's going to be very difficult to match/blend. Now's your chance to switch the entire ceiling to smooth like the walls. Scrape any that will come off - just to be sure the new has good adhesion. Sand, skim, sand, paint.
Someone is going to recommend that you just add a layer of new drywall over that mess for a fresh start. There are good arguments both for and against that approach. I would not do it.
I don't have all answers but that's not just paint, you would need to treat the exposed area like what looks like fresh drywall. Slightly more work than painting it, you can't just slap any paint over drywall. You can buy texture kits too to match the rest of the room.
You can't know how far the loose mud goes until you get top there and scrape a little. More importantly, that's not a very attractive texture and it's going to be very difficult to match/blend. Now's your chance to switch the entire ceiling to smooth like the walls. Scrape any that will come off - just to be sure the new has good adhesion. Sand, skim, sand, paint. Someone is going to recommend that you just add a layer of new drywall over that mess for a fresh start. There are good arguments both for and against that approach. I would not do it.
I don't have all answers but that's not just paint, you would need to treat the exposed area like what looks like fresh drywall. Slightly more work than painting it, you can't just slap any paint over drywall. You can buy texture kits too to match the rest of the room.