I always spray, roll or brush a bonding agent (Link or Plasterweld) into cracks or old plaster edges before taping. I embed the tape (paper for corners) in a setting-type compound, like Durabond 90 (sets in 90 mins or less). So the second coat can go on the same day. For second coats you can use another setting-type compound, Easysand (setting time @ 90, 45, etc), or regular green-lid drywall mud. Finishing touches with regular mud, for ease of sanding. Since it's a ceiling corner, it would be all right to use the dust-reduced type of mud, which I do not recommend for general work as it is very soft, but at a ceiling it wouldn't see any rough handling. It could, of course, all be done with ordinary green-lid mud, but I have had a great track record with durabond for old plaster repairs. Casey

Wet the area to soften things up, push it down and put a coating of joint compound over it. See if that will get it. I don't know how much luck you'll have with an epoxy, but good luck

I have the same problem on my second floor. Cracks show up in the winter, & mostly close up over the summer. In my case it is caused by the ceiling drywall not being secured tightly to the bottom chord of the roof trusses along the edge. Cheapskate builder's drywall crew used roofing nails to tack up the perimeter & didn't get it tight everywhere. Unfortunately in my case screwing the drywall causes the corner tape joint to completely pull apart. So as I've redone rooms I've gone up in the attic, shimmed the drywall tight to the roof trusses, then re-screwed the ceiling along the perimeter. In rooms where I've done that, the cracks have not reappeared.

I agree with Eandhl. Look at the difference in those two corner constructions and you'll see what she is talking about. I wanted painted too and I hated the look of those cracks in the displays. But those displays were not custom lines and I had other issues with the quality. I made sure I had an expert painter doing that work and I'm just not worried about it. Breeezy, you're going to love Clare. Laul, I can't tell you how it will look years down the road but I have no regrets. Don't let anyone talk you out of what you truly want. It's your kitchen.