If anyone out there is having issues on a #homelab #Proxmox machines with #Intel NIC's... In my case on a couple of #Lenovo M710q's with #I219-V, an Intel NUC10i3FNB with the same, and a #Protectli VP2420 with 4 * #I225-V. The solution for me so far (and I've not seen any performance impact though I've not _really_ looked hard so don't trust this for production) is popping the below after your 'iface eth0 inet manual' line. In my case of course I'm hanging everything else off a bridge onto that interface (vlans and what have you), or passing the PCI-E device to a VM, so adapt as you need. This came from a site somewhere but I cannot find the source any more.
post-up /usr/bin/logger -p debug -t ifup "Disabling segmentation offload for ${IFACE}" && /sbin/ethtool -K $IFACE tso off gso off && /usr/bin/logger -p debug -t ifup "Disabled offload for ${IFACE}"


