atmel-samd: SAMD51 boards stopped working with Thonny after 10.0.0-alpha.6

A user in discord was not able to save files with Thonny on PyGamer with recent versions of CircuitPython. Testing showed 10.0.0-alpha.6 works, but alpha.7 does not.

I tested RP2040,  ESP32-S2, and nRF52840, so this seems confined to SAMD. They don't have this problem and work fine with 10.0.1. I tested with a clean CIRCUITPY.

EDIT: still present in 10.0.3