SAL9K
Regular Contributor
It's not clear how you're iperf3 testing is being done... are you doing LAN<->LAN, or WLAN<->LAN/WAN?You're talking about a WiFi interference issue. I'm talking about Ethernet to Ethernet connections. I found no difference between USB 2.0 or 3.0, with or without a USB drive plugged in. The OP said he doesn't have a USB drive plugged into his router.
-- I'm doing WLAN<->LAN
-- Sounds like @road hazard is doing WLAN<->WAN