virtualbox guest display corrupted
updated to virtualbox 6.1.14 after being locked out for a while due to lack of HMA support. guest video output is corrupted immediately after the boot PROM hands over to any bootloader. vbox RDP output is also affected.
a more visible test would be to boot anything like solaris or opensolaris text boot (/etc/bootenv and friends handing over to the older red/green/blue installer)