I got a Xiaomi Mi AIoT Router AX3600 and it's on version 1.0.103. I tried to downgrade to the version (1.0.17) that has the bug for the back door and it seems to fail saying there is something wrong with the image.
I guess maybe they don't allow for downgrading any more to that version?
Looks like I have the wrong version of this router, it's the wrong one and it's not supported. Arg it's still so impossible to figure out supported hardware after all this time