Sorry I didn't respond earlier. Mine isn't a T2 Mac. Also, I've actually been doing some distro-hopping in recent days --- switching among Fedora, the Arch-based CachyOS, and the Fedora-based (and very-early-stage) RakuOS --- and the sleep problem has been consistent among all three. I also have tried Debian, and Debian-based distros, in the past and seen the same issue. I have a nagging feeling that it's something really simple but have no idea what.
I've also been frustrated by the whole old-Mac-on-Linux problem with internal speakers, as I've written before: