Dell T420 sever; BCM5720 interfaces are gone after upgrade from 19.10 ifconfig lists only "lo" and "tun0"
/etc/netword/interfaces show "auto lo em1" and "iface em1 inet static" ... (with settings)
lspci proves that the ethernet adapters are there, how can I make them be used by Ubuntu 20.04 (server)
I solved it by adapting instructions from https://linuxconfig.org/how-to-switch-back-networking-to-etc-network-interfaces-on-ubuntu-20-04-focal-fossa-linux