@poddingue
Huh.. Good catch.
I set all of the VMs to restart, and now it does make maintenance mode possible, on the host.
However, when we go into licensed/paid production (soon tm). It would be an absolute nightmare to try and find one VM that might not be on the right HA-plan... And it does kind of feel that Maintenance-mode should be compatible with whatever HA-plan is chosen regardless.
Perhaps there could be a way to assign a global/pool-wide HA-plan along with enabling HA alltogether?
Update: Shining light on that there is already a feedback-item, wishing for this kind of mass-operation for HA.
https://feedback.vates.tech/posts/45/bulk-operation-for-setting-vm-ha-option