I can confirm the issue after a fresh install of Lubuntu 20.04 on an old Asus X201E.
I could revert the behaviour to normal deleting adm and sudo from second user groups. It seems that Lubuntu 20.04 accepts only one admin... -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1875774 Title: Lubuntu 20.04 lxqt-admin-user Action (usermod) failed To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/lxqt-admin/+bug/1875774/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs