I had problems with 3.0 iso that I have reported here and hope will not be on the new 3.01 release. The simpler one but cause for many experienced users to complain was that SDDM had NUM LOCK key on by default. In many laptop models NUM LOCK key alters the character of many keyboard keys preventing authentication of some passwords.
The more complex to me was the unnecessary denial of 3.0 installer in putting grub2 at MBR in a computer with BOOT EFI Bios option. I was told to create a /boot/efi partition as the only option to have a bootable system. This created dual boot problems really difficult to face and certainly a cause for many users to give up from having OMV. The same configuration was not a problem for OMV 2013/2014 to work with MBR dual booting, so why would OMV 3.0 refuse to work analogously? Reference for the problem and the simple form to install grub2 in MBR in such a configuration is found at this reference,