Trunk from Dell to Netgear

Based on the details you've provided, we recommend ensuring that both switches are set to the same speed and duplex settings. Your Dell switch is currently configured for 10Gbps and full duplex. Please verify that the Netgear switch supports these settings and is configured accordingly.

Additionally, ensure that the transceivers and cables are compatible with both switches and are functioning correctly. A mismatch in these components can lead to the LOS issue you're experiencing.

Thanks for your reply. Have checked these, the SFP on the Dell is 10G and running at 10G as per the config. Here's the transceiver properties output: 

Tw1/0/3   SFP+    10GBASE-SR            CN04HG001CB10KR       Yes

Similar story on the Netgear (the "yes" refers to it being supported):

2/0/52   NETGEAR          22     22     -      3VA16B5J00430    AXM763             10300 3000 10GBase-LRM              Yes      10G

Running at 10G full-duplex is the default for the Netgear port, hence no config. Cable-wise I've used several known good cables on both ends, confident it's not a cable issue.

I still get LOS from the Dell though:

Tw1/0/3   25.5 3.258       5.7  -2.398 -40.000 No    Yes

Any other ideas?

Hello,
Unfortunately, I have no other ideas. We are talking about a configuration, that is why support on the forum is limited, it is something that usually our support does but for a fee.
In case you would like to learn more about it, I invite you to contact our support.
Thank you