Multiple internet connections through one router?

I'm wondering if it's possible to bridge multiple sources (e.g. spectrum + at&t) into one ethernet connection to then feed into my router? I definitely don't specialize in networking, so I can only think of 2 ways to achieve this: 1) A Windows box that has 3 gigabit ethernet cards, where I'd create a bridge for 2 of the connections and share them to 3rd one, which would then go into my router. 2) Basically the same thing but through a headless linux box that I'd manage via ssh.

Is there a better way to do that?