I think I am seeing something similar and it would be useful to have an official response.

I can neither set the speed to auto nor set it explicitly to some speed other than 10G. (I don't have any LAG.) I get an error mesasage when I try.

If the SFP+ ports only support 10G, that would explain it. Except that right now I have a 10G port which I know for certain is connected to a router which is only 1G. So I suppose another potential explanation is that this setting is ignored and the speed is always implicitly "auto". But if that is true then why does this web interface exist?

(What I was hoping to do was set the port to 5G because that will run over Cat5e.)

(I have firmware 1.20.0 Build 20231011 Rel.42220.)

I'm away from the switch right now, but here's a picture of what I was doing:

┌─────────────────────────────┐
│   TP-Link consumer-grade    │
│        Wi-Fi router         │
└─────────────────────────────┘
               │              
            1G │ Ethernet
               │               
               ▼               
┌─────────────────────────────┐
│         TP-Link 10G         │
│         Transceiver         │
└─────────────────────────────┘
               │               
               │               
               ▼               
┌─────────────────────────────┐
│           SX3008F           │
└─────────────────────────────┘

This is just for experimenting with the switch while I wait for a 10G router. But it does work.

The SX3008F reports that the port is running at 10G and will not let me set it to anything else.

The SX3008F also reports that the port is running in fiber mode, which is… not correct.

As I remember, no port, with or without transceiver, would let me set its speed to auto or 5G. I did not try 1G yet.

I am back at the switch. I have tried some experiments based on your suggestions.

Experiments

All ports (regardless of transceiver):

• I can set the speed to either 1000M or 10G.
• Attempting to choose any speed other than 1000M or 10G produces an error message.
• Speeds which are not available on the switch should not appear in the human interface.

A port with TL-SM331T (1000M):

• 10G makes no sense!
• Nevertheless, when the port is set to 10G it communicates over 1000M Ethernet just fine.

A port with TL-SM5310-T (10G/5G/2.5G/1000M/100M):

• While the port is set to 10G, I can connect a 1000M device and it works fine.
• I happened to be connected to this port when I switched from 10G to 1000M. I could no longer use the web admin interface after this. I did not investigate further. (I merely moved the cable to another port.)

Impressions

• It seems to me it must be that on this page one is setting the maximum speed of the port. If this is true, it should be clarified in the human interface. However, "Auto" makes no sense as a maximum speed, so it's possible i still do not understand.
• The fact that I can connect to a 10G port at 1000M tells me the transceiver must be quietly performing "auto" speed negotiation. If this is true, it should be clarified in the human interface.
• As-is, this page of the web admin interface serves no purpose for me. I might as well leave everything set to 10G all the time. I suppose it's possible that setting a port with a 10G transceiver in it to 1000M may actually limit the speed, but if that's all this page does, it is a lot more complicated than it needs to be.

Hopes

• I hope this 10G transceiver also works at 5G like it says on the page for TL-SM5310-T.
• I hope the human interface improvements suggested above are made soon.