I tried an online update and afterwards it wouldn't boot (stuck on "booting..." screen and et9x00 displayed on pvr).
I tried manually flashing the update using an usb stick. The flashing worked, but the booting problem remained.
Solution:
I downloaded the previous image et9x00-20191215, flashed using usb, and this flashed and booted ok.
Looks like my hardware is incompatible with the et9x00-20191216 release.
Solution: Use the openpli-7.2-release-et9x00-20191215_usb.zip image for xtrend pvrs for the time-being.