I'm not the OP!

Someone mentioned on Github that it breaks sound in SFOS too, but that really is not my case. Have you tried installing pactl? I don't know if this is device-related, or depends on what I configured in my container. Do other Pro1 owners observe sound broken in SFOS once LXC is running, and do they have sound in their LXC container?

This is a real rabbit hole but you can start by just installing xev with "sudo apt install xev", then execute xev in terminal, focus the white window, and type on keys. You'll see some (very) verbose output in the terminal. There are xev alternatives that might be a little less verbose or show different information. From there, since I haven't found a solution, I can't really give any instructions, but tools that might allow customizing how keys are handled in LXC include setxkbmap (which operates on xkb layouts), xmodmap (which I think is ignored in LXC due to the fact that we use Xwayland and not just X), kmonad (which I could compile successfully, but couldn't make it read my /dev/input/by-path/keyboard-kbd that I manually mounted in my /var/lib/lxc/debian-sid/config; probably a permission issue).