I also have that problem on 8.4.1 . i also applied the patch as said :
my /etc/network/interfaces:
auto lo
iface lo inet loopback
iface eno2 inet manual
offload-gso off
offload-gro off
offload-tso off
offload-rx off
offload-tx off
offload-rxvlan off
offload-txvlan off
offload-sg off
offload-ufo off
offload-lro off
auto vmbr0
iface vmbr0 inet static
address 192.168.1.4/24
gateway 192.168.1.1
bridge-ports eno2
bridge-stp off
bridge-fd 0
offload-gso off
offload-gro off
offload-tso off
offload-rx off
offload-tx off
offload-rxvlan off
offload-txvlan off
offload-sg off
offload-ufo off
offload-lro off
iface wlo1 inet manual
the log :
Apr 13 21:28:12 vrProxmox pvedaemon[154583]: <root@pam> successful auth for user 'root@pam'
Apr 13 21:35:04 vrProxmox pveproxy[156592]: worker exit
Apr 13 21:35:05 vrProxmox pveproxy[1219]: worker 156592 finished
Apr 13 21:35:05 vrProxmox pveproxy[1219]: starting 1 worker(s)
Apr 13 21:35:05 vrProxmox pveproxy[1219]: worker 209836 started
Apr 13 21:35:22 vrProxmox kernel: e1000e 0000:00:1f.6 eno2: Detected Hardware Unit Hang: TDH <8> TDT <56> next_to_use <56> next_to_clean <8>buffer_info[next_to_clean]: time_stamp <103160197> next_to_watch <9> jiffies <103160cc0> next_to_watch.status <0>MAC Status <40080083>PHY Status <796d>PHY 1000BASE-T Status <3800>PHY Extended Status <3000>PCI Status <10>
Apr 13 21:35:24 vrProxmox kernel: e1000e 0000:00:1f.6 eno2: Detected Hardware Unit Hang: TDH <8> TDT <56> next_to_use <56> next_to_clean <8>buffer_info[next_to_clean]: time_stamp <103160197> next_to_watch <9> jiffies <103161480> next_to_watch.status <0>MAC Status <40080083>PHY Status <796d>PHY 1000BASE-T Status <3800>PHY Extended Status <3000>PCI Status <10>
Apr 13 21:35:26 vrProxmox kernel: e1000e 0000:00:1f.6 eno2: Detected Hardware Unit Hang: TDH <8> TDT <56> next_to_use <56> next_to_clean <8>buffer_info[next_to_clean]: time_stamp <103160197> next_to_watch <9> jiffies <103161c80> next_to_watch.status <0>MAC Status <40080083>PHY Status <796d>PHY 1000BASE-T Status <3800>PHY Extended Status <3000>PCI Status <10>
and it continue like that until you reboot
i am now trying the solution from sudsy from here
https://forum.proxmox.com/threads/system-loses-networking.98705/
i also have a VLAN tag from my router, maybe thats the problem.
and added this to the /etc/network/interfaces:
auto vmbr0.40
iface vmbr0.40 inet static
address 192.168.1.4/24
gateway 192.168.1.1