@ryo @root I just use scp (sftp also works). And you can connect the computers directly, with an ethernet cable, but you need to set up a static IP address on both machines (they have to be different). Also, can't you connect two computers together with Firewire or Thunderbolt? I think those ports may be able to do that, but I have never done it and never even had Thunderbolt. But I think those just have built-in networking, so you may have to set up the static IP anyway.

Anyway, I don't know how to do this on shitty retarded distributions that removed ifconfig, which is most of them. They replaced it with ip. With ifconfig, it's just ifconfig, then the name of the ethernet inferface (you get it by running ifconfig with no arguments, it always begins with e), and then the address (it can be 10.0.0.1 and 10.0.0.2 on the other machine). With ip, I think it's similar to this command:
https://wiki.archlinux.org/title/Dhcpcd#DHCP_static_route(s)