Very normal behavior. The main thing is that the fish is eating. Try to feed several times a day but just small amounts. You can also try different foods, and I'd highly recommend adding small clams in the shell for the angel to pick / eat on. The clams worked better for me than anything else, as I could leave them in the tank for a while and let the angel pick as it was comfortable doing. The last thing you want to do is try to force things and stress the fish. Give it time to adjust.
For what it's worth, my regal behaved the same way. It ate very little for the first 7 to 10 days. Then one day it just started eating aggressively, and I couldn't believe what a pig they can be! After your fish starts eating normally, I'd also recommend you leave him in the QT for another week or longer to fatten him back up before introduction to the main tank. Most likely the transition to a new community tank will start another stress period for the angel where he won't eat or will eat reluctantly. Regal angels can be pretty timid, so if you have aggressive tank mates, you will want to monitor the interaction to be sure they don't stress the regal too much. I had a purple tang that I added months AFTER my regal angel, but the purple was being too aggressive to my regal and stressing it where it started acting stressed and eating less. I had to intervene by putting the tang in a QT tank twice and reintroducing before things finally got sorted out.