Phones that don't get updates for 12 months also should be required to unlock their bootloaders, so a 3rd party ROM can be installed, or at least Magisk can be loaded.

Mediatek devices are beyond hope, but some could be saved this way that are otherwise trash.

Mediatek has always been more open than others -- the bootloader wasn't even locked on most generic Androids, and SPFlashTool easily gets around it. For the newer devices, there's MTKClient: https://wiki.postmarketos.org/wiki/Mtkclient