So I'm recycling this bug report for what we discussed the most in comments, how to get the "lxd" group on our users' system.
The current recommendation I believe is to have snapd always create it (needs to be a system group!) and then figure out a clean way to address such needs moving forward.
All the other bits that were raised in this bug have been split into separate bugs (look for the lxd tag).
So I'm recycling this bug report for what we discussed the most in comments, how to get the "lxd" group on our users' system.
The current recommendation I believe is to have snapd always create it (needs to be a system group!) and then figure out a clean way to address such needs moving forward.
All the other bits that were raised in this bug have been split into separate bugs (look for the lxd tag).