I get very annoyed every time Opera GX updates because the update webpage always opens up the sidebar that I don't use and want to keep hidden, and it happens quite frequently. I installed the Block Site extension just to block that page entirely. Please remove whatever code is in the webpage or the browser that forces a closed sidebar to reappear. Thanks.

@mddarkness2009 Not automatically, but there is a small speaker button on any tabs with videos/music playing that you can quickly press to silence them.