Thanks for this clarification. So OMV4 is NOT (official) stable/final at this point and OMV3 is the recommended version. The "OMV4 stable"-tags in forum are also gone now. Is there any eta for OMV4 final on the horizon?
OMV 3 is NOT RECOMMENDED. Its underlying Debian Jessie is beyond End of Life. And AFAIK there will be no more updates to OMV 3.