Turns out I edited the wrong platform.txt
.arduino15/packages/Seeeduino/hardware/nrf52/1.1.8/platform.txt
instead of
snap/arduino/85/.arduino15/packages/Seeeduino/hardware/nrf52/1.1.8/platform.txt
But now a new error on the same line:
/home/alex/.local/bin/adafruit-nrfutil --verbose dfu genpkg --dev-type 0x0052 --sd-req 0x0123 --application /tmp/arduino_build_509375/sketch_jul24a.ino.hex /tmp/arduino_build_509375/sketch_jul24a.ino.zip
fork/exec /home/alex/.local/bin/adafruit-nrfutil: permission denied
Error compiling for board Seeed XIAO nRF52840 Sense.
The file has execution permission for everyone
alex@Ubuntu:~$ ls -l /home/alex/.local/bin/adafruit-nrfutil
-rwxrwxr-x 1 alex alex 216 Jul 24 11:34 /home/alex/.local/bin/adafruit-nrfutil
and I can invoke this from Linux trerminal
alex@Ubuntu:~$ /home/alex/.local/bin/adafruit-nrfutil
Usage: adafruit-nrfutil [OPTIONS] COMMAND [ARGS]…
Options:
–verbose Show verbose information
–help Show this message and exit.
Commands:
dfu This set of commands support Nordic DFU OTA package generation…
keys Generate keys for signing or generate public keys
version Displays nrf utility version.
alex@Ubuntu:~$