networking – Ubuntu Server 20.04 no internet connection/network unclaimed

I tried installing Ubuntu Server 20.04 on my Gigabyte B550i with an Realtek Ethernet Controller and wireless. I want to use ethernet (I don’t care about wireless), but I wasn’t able to set it up during installation and cat /etc/netplan.*yaml returns just:

      version 2

and lshw -C network lists both networks, the ethernet one unclaimed, the wireless one diabled. /etc/network/interfaces is empty, I tried different file contents, but nothing worked.

What am I doing wrong? I tried installing some kind of drivers, but didn’t succeed.