Yes it's not working very well. You have to wait a lot, just to be sure, then unplug the power.

I don't see anything about it in the changelog, seems this issue is not going to be fixed. Unfortunately EEE is a mess and this kind of issues are very frequent with most NICs. Same on latest generation Broadcom SoC for STB, latest drivers. Nobody is willing to fix it, the solution is always the same, disable it. If your NIC is Realtek and you are using Windows download the latest drivers from Realtek website, go to Device Manager, find the NIC in Network Controllers, go to Advanced tab, set: Energy-Efficient Ethernet, Green Ethernet, Gigabit Lite to Disabled

Do you mean Realtek? Or Maxlinear? To be honest never had problems. I could only notice this weird higher latency while running iperf. It's a signal that something doesn't work as it should but quite a corner case, I guess nobody is playing games while running iperf :)

AFAIK it's a direct connection without any splitter, there's no Cable signal running in parallel. I have to open the socket and check exactly what's inside to be sure. I'll let you know.

Yes if it's an unmanaged switch with EEE you are doomed. But even if you have one without EEE, like my QNAP QSW-1105-5T, and you don't have any network disconnection doesn't mean that it's working properly. Better to disable EEE in any case, at least till it's fixed. BTW when running iperf the latency it's not 3ms, wanted to say one-digit, fluctuates between 6ms and 8ms mostly.

I did a check since I have a Realtek 8125 2.5G NIC (MSI B550 Unify-X) connected directly. I've run a long iperf test to my NAS which is connected at 2.5G via a QNAP switch to the other MA2500D. Couldn't reproduce the brief disconnections with EEE enabled. But then I left a ping running toward my NAS server while running the iperf transfer and noticed the latency increasing from 3-4ms to 40ms. Disabling EEE on the NIC brought back the latency to 3ms while running iperf. It's definitely recommended to disable it in any case.