Just an update to give a little more information.
1st These x553 ports work perfectly on kernel 5.15.152-1-pve, in fact I run 2 in a bonded pair, over 2 DACs to a MikroTik CCR2004 (MTU 9000), tested with multithreaded iperf2 (not using --bidir using -R to test receive only) in both directions these are results:
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However the problems start as soon as I switch to any version 6 kernel, Worst results are seen with a 10GTEK Intel Compatible 10Gb SFP+ RJ45 Module connected to a Netgear XS712T 10G switch as I posted previously, the DACs fair better on my MikroTik giving full 10G when sending traffic but about half 4-6G when receiving. I'm hoping a fix will come along in the future which I will test and post results again but until then I'm stuck on version 5 kernel.
Has anyone got these working on version 6 kernel with full 10G in both directions? Is so what combo of Modules/DAC/Switch kernel and driver?