@Hadden89 Seems there was something bugged for me with that extension after updating it cuz it just wouldn't open if I clicked on it from the extension icon. But I reinstalled it and it's working now.
But the side panel is still getting blocked, and the other 2 extensions are as well. I had assumed getting blocked by Vivaldi was intentional and didn't consider it could've been a bug. Regardless, it would be nice for a fix either way.
I don't often post in any forums but this bothered me enough to. But with some side projects/tools I've been messing with I have less need for the HLS streamers and the more important one seems to be working now so I'm grateful your response was able to help me fix that.
Edit:
The video downloadhelper seems to have broken again, and I read the recent comments on it so that extension just seems to be bugged after their last update and that's on them, not Vivaldi.