Why do you advise against using a Raspberry Pi or other ARM device as a UBOS development machine?
The Raspberry Pi is fine to run UBOS on. But we recommend you use a PC or virtual machine to develop for UBOS, for these two reasons:
Development is not much fun on a slow device, and ARM-based devices like a Raspberry Pi are substantially slower than a modern PC.
The Raspberry Pi and other ARM devices use an SD Card as its hard drive. SD Cards, unfortunately, do not lend themselves to repeated compile cycles, and have a habit of dying when over-used, perhaps taking your code with them.
If you must use an ARM-based device, we recommend that use use a modern Raspberry Pi with multiple cores, and at least you store your valuable code on an external (USB) disk instead of notoriously unreliable SD Cards. Compilations will be faster, too.