This bug is now closed as Invalid since it does seem to be the issue described in comments #2 and #3. So not a bug, but an interesting point of confusion that other users might encounter. To "fix" it though would be an enhancement request. If you like then we can turn this into an enhancement request...
** Changed in: mutter (Ubuntu) Status: Incomplete => Invalid -- You received this bug notification because you are a member of Ubuntu Desktop Bugs, which is subscribed to mutter in Ubuntu. https://bugs.launchpad.net/bugs/1888800 Title: Resolution of external monitor goes back to its default resolution when laptop lid is closed To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/mutter/+bug/1888800/+subscriptions -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs