Hmm. In /usr/share/bash-completion/completions/ is a set of symlinks that just points (eventually) at /var/lib/snapd/snap/snapd/current/usr/lib/snapd/complete.sh
That file seems to not really have anything explicitly to do with lxc per se. Looks like it builds a command for snap run near the end.
Feels like I’m going down the wrong path.