I'm using the browser, chrome on mobile.
The website experience is abysmal for any stream that uses dual streaming for horizontal and vertical video.
It's impossible for me to choose one and it's auto-selection is just completely i competent. I'm only using locked-landscape on my phone yet I struggle immensely with choosing anything reasonable. I've set the chat settings to minimum, yet the chat takes literally 80%-90% of my screen and I'm given a tiny portrait mode video which no human being could plasuibly want.
Someone pushed this feature broken. It's not minor issues with viewability it's MAJOR issues.
It's incredibly strange how twitch chooses when to switch around also. I did get my stream working as I wanted for about 8 seconds before it switched to the broken portrait mode. No orientation change to the phone was made and as I said I'm locking my phone orientation.

Sorry for making such an overbroad complaint but this is too much to begin reporting accurately. The first step to being able to make sense of anything would be for me to be able to tell the app that I don't want anything but landscape. So I at least get the right dimensions for the screen. Then I could complain that the chat is too big and doesn't respond to me asking for minimal chat.

As it is I can't watch twitch.