Rotate HyperPixel but not HDMI

I’m using a HyperPixel 4.0 on a Pi 3 A+. I managed to get both the HDMI (with a 720p monitor) and the HyperPixel to work at the same time by adding max_framebuffers=2 to /boot.config.txt.

I’d like both to run in landscape mode, but by default the HyperPixel runs in portrait mode. And if I set display_rotate=1 in the config.txt file, it rotates both displays.

Is there a way to rotate only the HyperPixel display?