I got it. Eureka.
I am monitoring all my devices via SNMP and have Observium running on my second HP. That is just for Docker containers and it serves me really well.
Solution:
- download the Windows Server 2019 Evaluation .iso and boot it up from a disk.
- I installed it on my cache drive, since that is easily redone with unRAID.
- Install the latest HPE Service pack on your Win Srv system and it will install and activate the Agentless Management Service on the server, and that will activate it again on iLO (4 in my case)
- Now everything is coming through again and I can see my HDDs, SSDs, and NVMes. Also, the RAM again with descriptions, temp., speed, etc.
...and it only took me a day to figure everything out
Now I am switching back to my unRAID USB stick to boot and everything is fine again.