Found this diff when updating an old tree, ok?
Index: usr.sbin/tcpdump/tcpdump.8 =================================================================== RCS file: /cvs/src/usr.sbin/tcpdump/tcpdump.8,v retrieving revision 1.108 diff -u -p -r1.108 tcpdump.8 --- usr.sbin/tcpdump/tcpdump.8 31 Oct 2019 18:10:22 -0000 1.108 +++ usr.sbin/tcpdump/tcpdump.8 6 Nov 2019 12:12:54 -0000 @@ -146,6 +146,9 @@ searches the system interface list for t interface .Pq excluding loopback . Ties are broken by choosing the earliest match. +.Ar interface +may be either a network interface or a USB interface, for example +.Ar usb0 . .It Fl L List the supported data link types for the interface and exit. .It Fl l
