Power off K2
Open cover
Attach 3-wire USB cable (D+ D- GND type)
Attach USB cable to PC (also works with Windows 11)
Hold down button (S3) next to RP2040 USB header
Power up K2
Release S3 button
PC should have a new drive
Copy or drag the .uf2 firmware file to the drive
Power cycle the K2
The RP2040 firmware should now be updated and compatible with K2 core V8_RC18 and higher

Commands to try:

fpga list 3  
fpga status
fpga log
fpga list
fpga list 3                          (show what's in context 3, slot 3, "CNTX3")
fpga program 3 {file}                write a core file to SD card CNTX3 folder
fpga program 3 /dd/cores/core.bin
fpga flash 3 /dd/cores/core.bin.gz   write a core file to RP2040 Flash context/slot 3
fpga abort

