I had the same issue as Slartibartfast in that upgrading the Pi4 just caused Max2Play to crash when booting up. I didn’t play around much after that and went back to pCP.
I am surprised that your Pi4 is running that hot though, 76 degrees seems excessive. What sort of environment is it in? Is it a hot cupboard, is there a hard drive connected directly to it? Is it running LMS or just working as a player?
My Pi4 is running LMS but isn’t a player and ticks along at about 48 degrees in a hot cupboard. I’m using a cheap heat sink case which keeps the temperature quite steady. I don’t have a dac attached but I wouldn’t expect it to make that much difference.