@Cahlen
yes, I upload now all my new Videos from the new Xiamio Mi A2 Lite phone in 4K Resolution.. Yes, I used the Open Camera App, but their stabilisation feature in 4K Mode is not the best, so I put it afterwards through the Google Photos App Antishake filter that is really nicely adding nice stabilisation.
But the problem is, that the File sizes are pretty big then and it takes a lot time to upload... so I maybe will soon go back to 1080p, when I am back on the campground, where I only have 60 GB data traffic per month...