So the steps to reproduce this are somewhat unclear, so let me know if I did anything wrong:
1. Boot fresh installation of Lubuntu 20.04
2. Use lxqt-admin-user to create a second user (let's call it user2)
3. Use lxqt-admin-user to add user2 to sudo
4. Logout and back in again (yes, this is a requirement to reproduce— if you want, you can first remove user2's sudo and it will work, but then add it back and continue on)
5. User lxqt-admin-user to try to remove user2's membership in the sudo group (fail)
6. Try running pkexec against something. Since synaptic is well set up for it, this is a good example, so install synaptic and run `synaptic-pkexec` (fail)
7. Remove user2's membership in the sudo group for sure with `sudo usermod -G "" user2`
8. Try running the pkexec command again (success)
I did check this also against the adm group and it didn't seem to have an effect.
Anyways, I'm pretty sure the error, if anywhere, exists in lxqt-policykit. It's had like almost zero upstream issues, so that's interesting.
It's also possible this is a pkexec issue of some kind. It has caused many headaches for folks.
I'm updating my machine running off of LXQt's git master and we'll see if it behaves any better.
So the steps to reproduce this are somewhat unclear, so let me know if I did anything wrong:
1. Boot fresh installation of Lubuntu 20.04
2. Use lxqt-admin-user to create a second user (let's call it user2)
3. Use lxqt-admin-user to add user2 to sudo
4. Logout and back in again (yes, this is a requirement to reproduce— if you want, you can first remove user2's sudo and it will work, but then add it back and continue on)
5. User lxqt-admin-user to try to remove user2's membership in the sudo group (fail)
6. Try running pkexec against something. Since synaptic is well set up for it, this is a good example, so install synaptic and run `synaptic-pkexec` (fail)
7. Remove user2's membership in the sudo group for sure with `sudo usermod -G "" user2`
8. Try running the pkexec command again (success)
I did check this also against the adm group and it didn't seem to have an effect.
Anyways, I'm pretty sure the error, if anywhere, exists in lxqt-policykit. It's had like almost zero upstream issues, so that's interesting.
It's also possible this is a pkexec issue of some kind. It has caused many headaches for folks.
I'm updating my machine running off of LXQt's git master and we'll see if it behaves any better.