Thanks for your replies!
WOL in OMV -> Network -> Interface is currently OFF. Also testet ON but it makes no difference.
Autoshutdown shutdown command is set to "suspend".
WOL in the bios is ebabeled, too.
ethtool for the ethernet adapter shows the following - WOL is enabeled
Do the other WOL setting "p u m g" make any sense for my usecase?