My setup is similar like yours, unifi router is upstairs, and most of my networked entertainment is in my living room downstairs.

What I did was getting a gigabit powerline (https://www.lazada.com.my/products/tp-link-av1200-gigabit-passthrough-powerline-starter-kit-tl-pa8010pkit-i4784415-s5773352.html?spm=a2o4k.searchlist.list.6.52c677a6FKqBTt&search=1) and then buy a cheap 5 port gigabit switch and connect my tv, media center and avr to this switch. Streaming a full 4k movie from my NAS which is connected to the router upstairs is not a problem.