Hmm, well only netdev then again
Anyway, that there are no drops or errors showing could mean:
- kernel does not account error | drop frames due to some unset kconfig flag and those statistics are not available - but I am not sure whether there is a particular flag (similar to Where are iftop, iotop, nethogs and friends?)
- frames not being dropped by the TO kernel
- frames are somehow (erroneously) dropped by (potentially buggy) port driver (mvneta) and not reported to the kernel - but then it should likely happen also with SFP setup
- frames being dropped by the modem for some reason
Not sure whether worth the effort, a packet dump audit might yield some insight. If you are familiar with wireshark you could could do a remote ssh capture from the W10 desktop on TO’s eth2 port and see what happens to packets during the WAN iperf3 test.
Same for the modem (port) if it provides a ssh server.