Would be nice to have an option to schedule maintenance for all devices which are not part of any group. This way if you have a bunch of devices not in a group or someone has forgotten to put a trivial device in a group you could just select " ungrouped" devices when scheduling a maintenance window.
I recently ran into an issue where librenms was removing the “hardware” portion of the device details when it could not poll the device via snmp, this caused some issues with a group I have setup that is base on the hardware section (ubiquity wireless equipment) and these were cpe’s that really did not need to alert at late hours, this caused them to no longer be part of any group once that hardware information was removed. I ended up just putting them into a static group, but having “ungrouped” would be nice for this type of issue.