Yes, I think I've managed to solve it.
I created a resolv.conf file under a directory I use for various scripts and I copy that, overwriting the one in /run/connman, by putting this in autostart.sh.
cp -f /storage/.config/scripts/resolv.conf /run/connman/
I know it's a bit of a hack, but it seems to serve the purpose.
Edit: in case other people use Zomboided's VPN Manager for Kodi, the above hack survives disconnection and reconnection of the VPN. I guess the resolv.conf file is written by connman just at the execution of connman.service and no more until the next reboot, where we proceed to overwrite it once more.
hey could you happen to note what code is required that you have for the autostart.sh script, resolv.conf script and other scripts to prevent dns leaks? I'm also getting dns leaks