Hi again!
I first noticed this on my 19.1.1/LibreSSL (opnsense-patch 90c0c395 installed) with OpenVPN client for site-to-site doing fine for years.
Repeated resetting the connection (no useful entry in OpenVPN server log) with:
openvpn[59431]: disabling NCP mode (--ncp-disable) because not in P2MP client or server mode
...and afterwards trying to reconnect. Ok, I thought, let's have a look in the logs of the second machine I upgraded to 19.1.1 LibreSSL yesterday. And there where the same errors, but starting from December 2018, i.e. where I set up the machine with 18.7.10. So the problems apparently started with 18.7.10.
Any ideas what this could mean, a quick Startpage gave me nothing conclusive (as usual with tunnels and error messages...).
...although we are still on OpenVPN 2.4.6 this might be a hint:
"Please note that LibreSSL is not a supported crypto backend."
https://openvpn.net/community-downloads/
OMG...