Unable to look up screen scale and Unexpected physical screen orientation in Xcode 10

I've met the same problem. Finally I find out that this is because I accidentally resize the simulator's screen using my mouse cursor. By quiting and restarting the simulator my problem is solved.

Hope the aforementioned information helps.

This won't answer your original question, but it might relieve your eyes. A caveat to this answer however is that it disables all NSLog statements.

Do the following to suppress - all NSLog statements including - the warning: Unable to look up screen scale:

In Xcode, go to Product - Scheme - Edit Scheme, select 'Run' on the left side ...

... and add OS_ACTIVITY_MODE with value "disable" in the Environment variables section.

It could sounds dummy, but these warning appeared me after move the simulator previously rendered from the Macbook screen, to a wider external screen.

I solved it just restarting the simulator in the external screen. My 2 cents.