Can you please explain in what way uBlock Origin is neutered under Vivaldi?

Note that I am, despite your assertion, using the full uBlock Origin, not the Google-friendly uBlock Origin Lite. Proof:

I suspect you may simply be confidently incorrect, but I’d be interested to learn in what way uBlock Origin has been neutered.

You are also incorrect with your assertion that I “won’t try downstream Firefox products”. I stated that I used Librewolf for months, but finally had to drop it as the tradeoffs for privacy vs compatibility were prohibitive for my use case.

I’d also love to see the “relevant metrics” to which you refer, please.