Recently moved from Librewolf to Floorp (also based on Firefox). It is at least worth checking out I’d say, especially if you’re on Vivaldi specifically because you can’t find something which competes in customisation, workspaces, and sidebars and all.

Free tip: The stuff after ?si in the link you provided is just a shareID. It isn’t part of the link to the actual video, and serves no purposes but tracking.

Just the URL to the video looks like this: https://youtu.be/d-7o9xYp7eE

You can do ≈5 prompts in a chat before you need to reset if you don’t have an account.

Same here, except I’m on Firefish and I use it to view Mastodon and Misskey.