10M Port speed for m4300-96x - APM408C copper ports

It's quite interesting that neither manuals nor datasheets for that device mention anything else than "Ethernet" port, maybe that's considered normal in the AV space? Considering it's a piece of equipment with price tags above the 10k $ mark and marketed for professional 4k video cameras I'd be quite surprised, that they'd equip it with a 10M port as looks like current product as of writing.

Have you tried connecting it to another switch to see that if the link comes up, at what speed that it does so? Additionnaly you could check the switch logs on the M4300 to see if anything pops up. (Maybe you'd have to temporarily enable debug logging)

But yes, the APM408C modules wouldn't work with 10M only devices and it is not only a Netgear thing as there are other switch manufacturer who sell 10G switches not capable of stepping down to 10M. AFAIR it is an issue "caused" by the merchant silicon manufacturers gradually ending support 10M on switch chips thus switch manufacturers like Netgear can only follow suit.