It's great that this works but there are so many steps involved. I would like to see a tool developed similar to growpart from https://github.com/canonical/cloud-utils which would be able to perform all of these steps automatically with a simple package install.
Next to developing an x86 installer (which I don't actually think is that farfetched!) this would really help a lot of people on this platform.
See also: https://openwrt.org/docs/guide-user/advanced/expand_root