Wireshark - allow non-root user to sniff USB traffic
I solved it... running
sudo setcap CAP_NET_RAW,CAP_NET_ADMIN,CAP_DAC_OVERRIDE+eip /usr/bin/dumpcap
adds the CAP_DAC_OVERRIDE property to the dumpcap program. This allows it to bypass the usual restriction checks for reading and writing to interface devices (if I understand it correctly)