I'm still working out why the script from the wiki doesn't work. I was able to plug in a monitor to see the boot, and it hangs at "waiting for root partition at /dev/mmcblk0..." on the first reboot after running the script provided in the wiki.
yea...see...thats is exactly what i am saying. You can see that i have tried that script in the OP.
that script results in failure to boot on the raspi 5 on the first reboot. I have tried it several times. no luci, no ssh. it is hung up at boot with a message like "waiting for root at /dev/mmcblk1" or something. Because there is no ssh, the only remedy I have is reflashing but that takes us back to 100MB root.
but before reboot step i change UUID so can system boot again, because openwrt boot using UUID of disk, and after resizepart this uuid change to new value, so if you reboot the system it will try booting use the old value.