Luckily we had an agent baked in .deb format, managed to install it via SFTP+SSH. Can’t bake new agents, still have to get over my head with this new interface, in some things it’s better, in others I have a hard time finding stuff.
After an appliance restart we chose to rediscover services, added the new ones, now that error message is no more!
Thanks for your insight.
As separate news, going on the monitoring host properties, then choosing Hosts->Monitoring agent, the “This host has no Checkmk agents.” is still present. Guess that’s for another topic.