I encountered an error in your software (which I feel should be either detected before application starts or when connecting to VPN).
So if you have a system - for example: freshly installed Arch - that doesn’t have systemd-resolved enabled or any software that implements resolvconf. Connecting to any VPN will work, but you won’t be able to reach any resources through it.
In my example: I was using only NetworkManager.
While the fix on my side was quite simple - just enable systemd-resolved. I feel like this app should detect it and not silently ignore it.
The least you can do, is to report it in the logs.