I have lxd installed on an Ubuntu server in the cloud and on my personal Pop!_OS desktop computer. Both are installed using the snap package. The issue is that on the Ubuntu server, I have command autocompletion (pressing tab to complete lxd/lxc commands like lxc sta and hit TAB to produce lxc start) but I don’t have it on Pop!_OS.
I have no clue what that command does, as I have never seen a command with a dot like that in the beginning, but I did run it exactly as you said and it didn’t fix it.
Just noticed something interesting. Installed the juju snap and autocompletion works fine for it on the same computer. Thought it might be a general snap issue with Pop!_OS, but it is not.