Do you know what your infotainment software version is? If it's version -704 then it's known to be unstable.I also have this problem with my 2020 Outback Touring. Problem usually starts after I have switched audio functions a few times quickly. Only after shutting off the car, exiting, and then coming back several minutes later does the sound system "magically" work again. Weird. Does anyone know of a fix?
There is yet another software update to version -380 (it's newer and better than the old -504) that the dealer can install - it may help with stability. If not, then you might need a new CCU (the brains behind the infotainment screen). Your experience is not typical so it's possible you have a defective unit but the software update might help.