Board support for DFRduino M0 Mainboard does not install in Arduino IDE 2.3.6

I am trying to develop a sketch for the DFRduino M0 Mainboard, (SKU DFR0392) but cannot select the board from the Arduino IDE (v2.3.6).

When debugging the IDE, it produces the following error:

2025-11-17T14:05:01.655Z root ERROR Detected an error response during the gRPC core client initialization: code: 9, message: Loading index file: loading json index file c:\Users\mradwick\AppData\Local\Arduino15\package_dfrobot_index.json: parse error: syntax error near offset 0 of '{
 "pa...'
 

Any ideas?