I know almost nothing.

I have two computers right next to each other.

One is connected directly to my modem, and the other is connected to the router.

The modem has only two slots, one goes to my main computer, one goes to the router.

Is there a way to magically combine them? Do I need to plug my main computer into my router? Will that impact anything? Will it make things laggier? Slower? Latency? That’s a word I think?

The only thing I don’t want to do is change any router settings to impact the magical wireless settings

my main computer when i go into settings says its an Intel ethernet connection, and the spare computer says “broadcom netlink Tm gigabit”

imgur link trying to explain my setup https://imgur.com/a/EniA6eJ

im really just trying to get “input director” to work, as i want to set up my spare computer as a stream PC, but dont want to have 2 mice/keyboards on my desk.

help please and thank you.