Steam Link Issues with Hyperpixel 4

I have a raspberry pi 4 and the non-touch version of the Hyperpixel 4 in landscape mode. I just installed steam link and when it launches the first configuration/status screens are in landscape. When I launch into “Big Picture” mode, though, the image rotates to portrait and becomes completely illegible. I have big picture mode set to desktop resolution on the pi. How do I lock the screen in portrait/prevent the screen from rotating?

*edited first and second landscape from portrait.