Prioritising ethernet over wifi but still need wifi switched on
I have connected to my router with an ethernet cable to access the internet. If I have wifi switched on then I think my internet service comes through the wifi rather than the ethernet. But I need to keep wifi on to use other devices like Apple TV, Sonos system etc. AppleTV is my most immediate problem as working from home currently and need to mirror my laptop screen to a bigger screen. The AppleTV I'm using is a pretty old one. Many thanks to anyone who can help me work this out.
MacBook Air