Dangers of the lxd group
Ubuntu places users (unless otherwise specified) into the lxd group. This group is known to be a point of privilege escalation and should be removed from any user that is a part of it.
It is so popular that Linux-Smart-Enumeration even checks for it. Remove it from any user that has it assigned. Using adduser does not add the user to any predefined groups and should probably be used when adding new users.