nRF Sniffer for Bluetooth LE Wireshark plugin does not display any interfaces

There is an obscure error in the Wireshark plugin. The plugin loops over all serial interfaces and listens for the signature of the sniffer on each of them. However, for each serial interface, it attempts to create a lock file in /var/lock, which fails with a permission error. This makes the plugin conclude that the serial port is unusable and it skips it, even though the error really comes from the lock file. That manifests as no interfaces listed in ./nrf_sniffer_ble.sh --extcap-interfaces | grep ^interface (and also in Wireshark, of course).

The fix is not very clean but easy: edit SnifferAPI/Filelock.py and replace /var/lock with some other path that's writable by your user.