How to upgrade an x86/64 based router - Protectli FW6

I'm running 21.02.0 and installed the generic-ext4-combined.img.gz originally. Since this unit doesn't have flash memory I'm not sure if I can use the Flash Image option. Has anybody upgraded a Protectli or other generic x86/64 machine, and if so, are there special instructions.
Thanks.

Easiest way is to reinstall as per the original instructions: https://protectli.com/kb/openwrt-on-the-vault/

The following contains additional instructions, you may be interested in: https://openwrt.org/docs/guide-user/installation/openwrt_x86?s[]=x86

sysupgrade just works on generix x86 too. but you can try the process first in virtualbox.

if you don't mind having two parallel openwrts installed, try Sysupgrade help for x86_64 - #14 by frollic