But will you gain anything by building for it? Will you see noticeably more users or people choosing another alternative because you didn't specifically building the app for Duo? At least if it doesn't outright break.

I would get a little bit of joy if a duo user noticed the effort I put into making my app work well on their device. Why put effort into anything? Your take is bordering dangerously on cynicism. :)

You could say this about every QoL feature though. That’s not a reason to not do it though, it adds up and at some point other apps that do bother to make their apps as good as possible will become more popular than yours.

As a user, this attitude makes me sad.

As a professional programmer, it at least gratifies me to know this is the attitude I'm competing against.

Can two people use opposite sides while in tent mode? Because that makes for some fun in-person games.

Duo users also likely have disposable income to spend on in app purchases, maybe click on ads to purchase things, and other monetization. So I do think it's worth building for it.

But will you gain anything by building for it?

Nothing ventured, nothing gained.

Will you see noticeably more users or people choosing another alternative because you didn't specifically building the app for Duo?

I haven't done iOS development in a long time, but my understanding is that if your iPhone app is designed well and uses all of Apple's recommended methods, adjusting for different screen sizes and orientations is fairly easy.

If you decided to go cheap/easy/dumb from the outset, then you made your bed, and now you get to lie in it.