The only real way to play full co op is using the Seemless Co-op Mod. Also disables other players jumping in to kill you. You would have to play on PC though.

Dolphin sometimes takes 2-5 seconds to open on my gaming PC, whereas Nautilus (Gnome Files) is usually done before I’ve even let go of the click.

You might need to look into this more.

It opens instantly on my gaming desktop, Microsoft Surface 7 Pro, and ASUS ROG Strix