Side Panel working after re-starting web browser.
https://files.mastodon.social/media_attachments/files/109/473/992/872/001/624/original/cca61c7f024ce653.png
So in order to get @Vivaldi's side panel to work, you *must* re-start your web browser after signing into their Mastodon instance.
See, after I did that, it displays fine.
Another interesting thought: after signing into Vivaldi Social, the width is now more "sane".
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