iPad app on Mac - Fix window aspect ratio

I'm developing an app that works on iOS and iPadOS in Portrait mode only. I'd like it to be able to run on Apple Silicon Macs as well, but when I try running it on my Mac, the application screen it resizable to any size and any aspect ratio.

(Oddly, it works fine in visionOS, where the window can be made bigger or smaller but always maintains a portrait aspect ration.)

Is there some way I can have the aspect ration fixed when the app runs on macOS?

Thanks!