I was able to participate in OpenVMS V9.1-A field test and install OpenVMS on VirtualBox.
There are a few minor considerations likeyou need to ensure EFI is enabled and there is a serial port mode TCP enabled.
To get to the boot manager you will need to navigate to the ISO (i.e. FS1) at the Shell> prompt such as FS1:\EFI\VMS\VMS_BOOTMGR.EFI
Once you have found the DVD boot device “DEVICES” and booted to it i.e. BOOT DKA100 you will need to switch to telnet on the specified TCP serial port i.e. 2023 as configured in VirtualBox. This will be the IP of the VirtualBox hypervisor. The installation option 1 will guide you through the rest of the installation.
One caveat to the installation is that if you are using PuTTY and cannot enter the SYSTEM password successfully, you must uncheck the “Return key sends Telnet New Line instead of ^M” checkbox in Connection > Telnet Configuration.
After the system is rebooted at the EFI shell you will need to manually enter the VMS_BOOTMGR.EFI boot manager again but this time boot to DKA0 where the OS is installed.
After boot, log in with the SYSTEM account and password set above, and you are ready to use the OS!