I return to this subject as I'm trying to wrap my head around /etc/resolv.conf.
As far as I can tell, that it's just a symlink to /run/connman/resolv.conf.
I have not abandoned my desire for using Wireguard but, in the meantime, I'm using the Kodi VPN Manager addon, which works.
DNS leaks problem remains and I tried modifying the above resolv.conf, finding a configuration for it that it works (no DNS leaks when connected to VPN, still capable of resolving when not connected).
I then set permissions for /run/connman/resolv.conf to 444 (read-only) and executed chattr -f +i /run/connman/resolv.conf, in order to make it immutable.
I rebooted and... the file had been modified back to its original state and permissions where once more 644 (read/write for the owner).
Is there a way around this, chewitt?