you can promote the secondary master. =>
I believe that it is possible to move the config master “role” from one server to another but I didn’t try that yet.
it could be something like:
deleting some directories, deploy director config to other master…
Icinga2 in case of monitoring is HA, but the configuration management is not HA and I think it doesn’t need to be. If your config master is dead your next step should be to restore the HA state of the cluster immediately because if your second icinga2 node is gone you have no monitoring at all.