It appears that the openvpn package is not actually installed, or since you are using a snapshot build, the package did not build correctly.
If possible, install the latest release build instead.
Can you share your "trickery"? I am also not able to get openvpn fully working. The reason I tried snapshot is because 25.12.4 is very slow on ovpn. https://forum.openwrt.org/t/slow-openvpn-25-12-4/250425
I am sure I must have some setting messed up.
You can check if openvpn is running.
ps |grep -i openvpn
2570 root 9052 S openvpn --config /var/run/openvpn.tun0.conf
4210 root 1240 S grep -i openvpn
If you want a stable/release build, don’t use luci-proto-openvpn. On release images the LuCI package is luci-app-openvpn (plus openvpn-openssl); luci-proto-openvpn is only in master/snapshot right now.
So either stay on snapshot and expect rough edges, or select your exact device in Firmware Selector with the stable version and add luci-app-openvpn/openvpn-openssl there.
Have changed now to release build 25.12. Previously, there was a snapshot installed, cause as new user i didn't know the difference between the images.
Connection from Router and devices behind to the OpenVPN Server works already, with packages openvpn-openssl and luci-app-openvpn.
VPN connection reaches the limit of WAN speed and CPU load at 15% is good.