If you manage to add the settings I added in libvirt to the XML file to your proxmox KVM guests (lookup the documentation for qm.conf and check the file in /etc/pve/qemu-server/VMID.conf. You may be able to pass those settings somehow there.
See: IP packet handling issues in virtio-net on certain OS/kernel versions on KVM VM - #9 by chani
However, I am not sure how to add these settings exactly; the nic Param does not allow it. Maybe using “args: …”. I verified that my fix works on another different host as well. But I’m using a libvirt-stack instead of Proxmox.
However, there might be an option superior to the above. And that one works with proxmox. Pass-through the NIC to the guest. Assuming you have a separate management link to your proxmox host this might be even performance-wise a better way to go.