I am not at home, but what I did was change the 99-default.link file. I found this from the two pages below. https://wiki.debian.org/NetworkInterfaceNames#CUSTOM_SCHEMES_USING_.LINK_FILES https://wiki.debian.org/NetworkInterfaceNames

Basically, by doing this, your nic cards will be forcibly named using the mac address:

#/etc/systemd/network/99-default.link
 [Match]
 OriginalName=*

 [Link]
 NamePolicy=mac
 MACAddressPolicy=persistent

Afterwards, you will need to reboot and then update your network config file to use the correct names. I don't ever change the network config with the GUI in proxmox as it has wrecked it too many times. I will update this reply again later with some more information on what to do.

Sorry, didn't make it home until today and not sure if you get notifications on edits. You will need a monitor and keyboard hooked up to your server as you will not have ssh access until the network config is "fixed". I would do the below with the GPU removed, so you know 100% that your networking config is correct before mucking about further.

Step 1 - Create 99-default.link file

Add a /etc/systemd/network/99-default.link with the below contents.

# SPDX-License-Identifier: MIT-0
 #
 # This config file is installed as part of systemd.
 # It may be freely copied and edited (following the MIT No Attribution license).
 #
 # To make local modifications, one of the following methods may be used:
 # 1. add a drop-in file that extends this file by creating the
 #    /etc/systemd/network/99-default.link.d/ directory and creating a
 #    new .conf file there.
 # 2. copy this file into /etc/systemd/network or one of the other paths checked
 #    by systemd-udevd and edit it there.
 # This file should not be edited in place, because it'll be overwritten on upgrades.

 [Match]
 OriginalName=*

 [Link]
 NamePolicy=mac
 MACAddressPolicy=persistent

Step 2 - Reboot and find new name of NIC that will be based on MAC

I forget if you have to reboot, but I am going to assume so. At this point, you can get the new name of your nic card and fix your network config.

1. ip link should list all of your nic devices, both real and virtual. Here is how mine looks like for reference, with the MAC obfuscated:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: enxAABBCCDDEEFF: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master vmbr0 state UP mode DEFAULT group default qlen 1000
    link/ether AA:BB:CC:DD:EE:FF brd ff:ff:ff:ff:ff:ff
3: vmbr0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
    link/ether AA:BB:CC:DD:EE:FF brd ff:ff:ff:ff:ff:ff

Step 3 - Fix your network config and restart network manager

You will need to edit your /etc/network/interfaces file so the correct card is used.

1. Make a copy of /etc/network/interfaces, just in case you mess something up.
2. sudo vim /etc/network/interfaces (or whatever text editor makes you happy) It will need to look something like below. I have to have DHCP turned on for mine, so your config likely uses static. Really all you need to do is change wherever it says enp yada yada to the enxAABBCCDDEEFF you identified above.

 source /etc/network/interfaces.d/*

 auto lo
 iface lo inet loopback

 iface enxAABBCCDDEEFF inet manual

 auto vmbr0
 iface vmbr0 inet dhcp
 #iface vmbr0 inet static
 #address 192.168.5.100/20
 #gateway 192.168.0.1
     bridge-ports enxAABBCCDDEEFF
     bridge-stp off
     bridge-fd 0

3. Restart your networking service. You shouldn't need to reboot. sudo systemctl restart networking.service

Step 4 - Profit?

Hopefully at this point you have nework access again. Check the below, do some ping tests, and if it doesn't work, double check that you edited the interfaces file correctly.

1. sudo systemctl status networking.service will show you if anything went wrong and hopefully show that everything is working correctly
2. ip -br addr show should show that the interface is up now.

lo               UNKNOWN        127.0.0.1/8 ::1/128
enxAABBCCDDEEFF  UP
vmbr0            UP             192.168.5.100/20 

At this point, if all is well, I would reboot anyways, just to make sure. If you add any GPUs, sata drives, other PCI device, disable/enable wifi/bt in the BIOS, or anything else that changes the PCI numbering, you don't have to worry about your NIC changing.