Here are some steps/observations I've had:
- I use a new incognito/InPrivate session each time I connect.
- I have used both DHCP and static IP addresses.
- I have put the router back in the original case to troubleshoot, but I have also tried with it in no case.
- I've used a second computer to see the logs through Wi-Fi and have a computer connected via the wired ports, so there is only one connection on each computer.
- I don't see anything in the kernel or system logs that jump out at me related to the br-lan interface or the individual ports (4 or 5, with the WAN port doing the same thing in LAN setup) when connecting the computer via a wired port.
- I have tried reflashing through the recovery GUI, which I could connect via a wired port, and resetting and reflashing the firmware via the "Backup / Flash Firmware" page. This did not change anything related to connecting via the wired ports. I also did notice that the DHCP range settings did not reset to the default.
- I've tried the firmware versions ending in 2023-01-12a, 2023-03-15, and 2023-06-01a.
- I've even tried removing the modem to try and isolate just the router to troubleshoot, which did not change anything.
- For power, PoE or adapter doesn't make a difference, although I can power up through the WAN port as a LAN port and still not get a network connection.
- I've also tried numerous premade and personally wired cat cables and tested them for valid layout and continuity to eliminate the cable as the culprit.
- I'm a novice at Wireshark, but it looks like the wired ports do not get to the point of doing more than the initial ARP broadcast before the connection resets.