Hi BD, I’ve been trying to track this myself.
I’m sure some parts of Northwest Sichuan and the boarding areas of Gansu and Qinghai, are closed now and might be thru summer. It’s often speculation and communication is not very clear.
There is some first hand news available on thorn tree.
I’m sure Dunhuang (炖煌) and Qinghai Lake (青海湖) are and will remain open, neither are very remote and both are extremely popular so would draw too much attention if they were closed. it’s the remote areas nearer the provincial borders that are closed.
Another (English speaking) sources might be travel agencies and hostels in the area. though they will only give you a current status and can’t guarantee the future.
I wouldn’t suggest traveling that way in a straight line over land to there from here, you’re bound to run into trouble, I don’t know if that’s what you’re considering.