SUMMARY
Trying to import a VPN connection from a config file that is owned by root will lead to the error message:

"Failed to import VPN connection: NetworkManager is missing support for OpenVPN"


STEPS TO REPRODUCE
1. Use the root user to create an empty file a.conf
2. Go to "Connections" section of system settings
3. Click on the Plus icon ("Add new connection") and in the resulting menu click on "Import VPN connection", then browse to a.conf from earlier and load it

OBSERVED RESULT
"Failed to import VPN connection: NetworkManager is missing support for OpenVPN"

EXPECTED RESULT
An error message that conveys the true nature of the problem, i.e. that the file mustn't be owned by root.

ADDITIONAL INFORMATION:
I got into this problem because my wireguard config file, which was located at /etc/wireguard, was not picked up by network manager (maybe this should be a separate bug report?). In order to get that file into my home directory, I had to be root.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 
(available in About System)
KDE Plasma Version: 5.27.5
KDE Frameworks Version: 5.106.0
Qt Version: 5.15.9