Thanks Valentine and everyone for such detailed replies. This is a thriving community!
Valentine, your power shield D beta looks great. I’m also keen to obtain one of these when they are available: https://community.simplefoc.com/t/simplefoc-driveshield-a-big-more-powerful-brother-of-the-simplefocsheild/5368/3
Neither of these have an embedded MCU, but perhaps I can get away with just using 2 Arduinos for now instead of one, or an STM32 Nucleo for the motor control plus an Arduino for the rest. The lack of 3 interrupts on the Arduino R4 is a real bummer.