> I tried to use picoprobe to debug an nrf52 chip, it failed to even detect it

I've literally got a Pi Debug Probe and a nRF52840 dev board on my desk, so I gave it a shot - and it works just fine. Make sure the core is awake when you try to connect for debug, or connect under reset; SWD goes to sleep with the rest of the chip.

> All that’s officially supported is using it to debug a raspberry pi

The Pi Debug Probe is a generic DAPlink probe, and will work for pretty much any Cortex-M part. I routinely use mine for debugging STM32 parts.