Sysupgrade help for x86_64

that's why i'd suggest to change grub to use simple partitions:

menuentry "OpenWrt-21.02.3-sda2" {
        linux /boot/vmlinuz root=/dev/sda2 rootwait   console=tty0 console=ttyS0,115200n8 noinitrd

PARTUUID in frequently changing hardware environment might make sense but it is a router, once it is up i don't want to add disks which might change disk order. so personally the very first thing i do is replacing PARTUUID. then can resize/add partitions as needed without jeopardizing hanging during boot because UUID i forgot to update (e.g. after partition resize).