Do you mean the iOS YT app? It's at most three, two if you allow a swipe. Swipe down on the video (moves it to a smaller view in the lower-right) > tap the X in the upper right of the video. Or tap the video (to bring up controls) > tap the down-arrow in the upper left (moves to the same smaller view) > tap the same X in the corner.
I am using YouTube website, on Firefox, GrapheneOS. If I click on youtube logo, it will close the video.
what am I missing from not using the app? It also continues playing when phone closed/black screen