I have installed the latest version of ProxMox onto a Dell R620 with a 2 port 10Gig NIC card and ProxMox recognizes it and shows it is connected at 10000Mb/ s, shown below:
CPU(s)
40 x Intel(R) Xeon(R) CPU E5-2670 v2 @ 2.50GHz (2 Sockets)
Kernel Version
Linux 5.0.15-1-pve #1 SMP PVE...