Notes
I was experimenting with taking 4K videos on my iPhone 11. It seems you can on a model from 11 upwards. Set it in Settings -> Camera. Sweet. So this is a 1 minute video I took this morning, and rendered it in Final Cut Pro. Lots of tricky stuff to get it right, as I set it to RGB/32 HDR-HLG and so on. But as you should see, YouTube now gives me the option to watch it in any resolution I like. Just select the cog wheel and you. can change it to suit your monitor or TV.