Seeed xiao usb serial support

Sparkfun SAMD21 boards have implemented SerialUSB to talk to the arduino serial monitor > I see no mention of any way to talk to the serial monitor through the USB on seed SAMD21 boards

How about fixing this?

We have the same implementation as Sparkfun.

Here is the example: https://github.com/sparkfun/Arduino_Boards/blob/master/sparkfun/samd/variants/SparkFun_SAMD21_Dev/variant.h

And our variant is:

Therefore you can also use SerialUSB if you like