How to stream 4K video from iPhone to Plex

I thought this would be easy but after searching the internet and these forums, I could not find an answer.
I have a Plex membership and I am trying to display 4K video I shot with my iPhone to a TV with Nvidia Shield/Plex.
I can stream it but it is extremely slow at buffering and almost unwatchable.
I tried to sync it to the server but I get “Syncing is not supported on this server.”
My plex server is a dedicated computer with a 8700k, 16GB RAM, and SSDs.

Basically, how do I download videos from my iPhone to my Plex server?
I also want to be able to backup all my pictures to my Plex server. Everything I Google just shows how you can download videos from Plex > iPhone. I want to go from iPhone > Plex.

I think I found it. All the directions use dated examples and the navigation is not the same.
It only gives me the option to upload the whole camera roll.
Is there a way to only upload selected photos and videos?

@dseg said:
I think I found it. All the directions use dated examples and the navigation is not the same.

I would say you would have to use a import client on your computer via your data and charge cable. Then add to your Plex storage area.

Maybe this free app.

I found it.
It started uploading and stopped after doing 100 photos of 6,000. Now it says “Nothing new to upload.”
And I’m not able to change of the settings to do anything, it’s all grayed out.
This feature is completely unintuitive.
Not sure what I am suppose to do now…