I think if we're comparing the easiness of repurposing an EOL phone, it is much better to just check the postmarketOS wiki for supported devices and pick one of those instead. They got great instructions for reflashing/jailbreaking the bootloaders etc.

And yes, you get a full blown Linux with it. So you can, like me, repurpose your smartphones into pretty much everything. I have removed their batteries and have them solar powered as Freifunk routers and even offline-ready kiwix media servers among other things.

[1] https://wiki.postmarketos.org/wiki/Devices