Personally, I tested three different chipsets (all by Realtek): 8152, 8153, and 8156. I’ve tested them with OpenWRT and with macOS. They all have the same problem. The problem is well documented and the Internet is replete with this information. But besides the fact that Realtek may have a bug in their chipsets, the very foundation of the USB3 based bus is the problem with consistent rx and tx rates. To have a reliable and consistent network connection, the network controller should utilize the PCI bus. This is what Thunderbolt based NIC dongles do. Thunderbolt provides direct PCI bus to an external device.
The problem with USB-based devices are not only NIC specific, but also storage specific, Wi-Fi adapter specific, etc. Anything connected to a USB3 bus suffers inconsistent speed. I don’t need to be dissuaded because I’ve tested this thoroughly with multiple adapters with OpenWRT, with VMWare ESXi. and with MacOS. In ESXi and macOS I had a benefit of being able to compare the consistency of USB3 based NIC dongles with Thunderbolt based NIC dongles. Even though USB3 NIC dongles can appear fine on iPerf tests, their performance degraded with time measured sometimes in days and sometimes in hours. It may not be critical with a dongle connected to a computer, but it’s critical with a dongle connected to a router or a server.
Now that the Raspberry Pi foundation has released Compute Module 4 and the matching official IO board where they removed USB3, thus freeing up the PCI bus and providing a PCIe 1x connector on the IO board, NICs directly connected to the PCI bus on an SBC like the Raspberry Pi CM4 has become a reality. That’s the way to build routers going forward, by utilizing one or more NICs with a direct connection to the PCI bus. Because of the lack of cases for CM4 with IO board v4 at the time of this writing, one can use the workaround that I discovered, tested, and am using now, which allows one to utilize a single onboard adapter for both LAN and WAN interfaces to eliminate the flakiness of the USB3 based Ethernet dongle.
I do wish the Raspberry Pi foundation would release another version is the Raspberry Pi 4B where they would remove the USB3 bus and replace it with a second PCIe-bus attached Ethernet Controller. Better yet, if they could put two multi-Gigabit controllers on the board for using it as a high-throughput router/firewall. I would pay $60 for a 2-port multi-gigabit (1/2.5/5 Gbps) board with 2 GB of RAM.