Hi @user706,
Thanks for reaching out!
So for question 1, this is just the generic compatibility check kicking in. By default, the device_type string for 32bit is raspberrypi4 on the RPi4, and on 64bit it is raspberrypi4-64 or raspberrypi4_64, depending on if you’re using mender-convert or Yocto to create the image. By setting MENDER_DEVICE_TYPE accordingly, you can make this match easily.
Question 2 is more tricky. The Raspberry Pi first stage loader does set up a few things depending on the arm_64bit setting. u-boot then needs to match this accordingly. So for such a 32bit->64bit upgrade, you would need to also upgrade the bootloader which is a potentially destructive operation.
Hence, the answer is a “can be done, but depends.”
Greetz,
Josef