I can not upload 4K 60 FPS video from Iphone 14 Pro to Youtube from PC (with Camera default settings).
Site says about unsupported format.
How to fix this without 3rd party apps?
Are you recording HEVC files? YouTube says it supports it, but that would be my first guess - try switching and see if it works...
From Apple's support page:
Go to Settings > Camera. Tap Formats. Tap Most Compatible.
YouTube recommend using H.264 files:
You might be able to convert your files to h.264 format using Windows' built in hidden video editor inside the Photos app (but I'm on a Mac so can't confirm).