Web layout MUST be made responsive to window width.
I don't know what window width Twitch imagines as a minimum, but it's clearly wider than my window width, as chat and the chat menu do NOT display on a channel page unless I maximize my window. This is utterly insane in 2023. The chat menu must ALWAYS show, no matter how narrow the window. I will not say how wide my window is, because my entire point is that it should not matter. The inventor of the WWW, Tim Berners-Lee, intended it to be device independent. That means that everything on the page should be accessible regardless of window width. This is Web Design 101, and anyone on your Web team who does not grok this should be dismissed as they are unqualified to be in the field at all.
Your current site forces me to 1)maximize my window (yuck, ugh, ****), 2)look for the chat menu, 3)pop-out the chat, and then 4)un-maximize to restore my desktop to sanity. Ridiculous hoops to be forced to jump through.
You absolutely MUST fix this. And fire anyone who doesn't "get" it.