Vivaldi is dead once uBlock Origin stops being supported. uBlock Origin is mandatory it today's internet, ignoring all the privacy benefits, it's a basic security tool at this point. They keep saying they have built-in ad blocking, but it's nowhere near half the functionality that uBlock Origin offers.
Signed, long time Vivaldi user.
We will keep Manifest v2 for as long as it’s still available in Chromium. We expect to drop support in June 2025, but we may maintain it longer or be forced to drop support for it sooner, depending on the precise nature of the changes to the code.
The most ironic part is that some are calling Manifest v3 as a win for security. Sure in the most basic view, it's more secure by default since it limits total access, but it ignores the simple fact why the broad access is needed in the first place. If you are trying to protect from sites that have broad access to tracking, be it malicious or abusive, you can't protect from it if your browser actively removes tools needed to protect from it. So in the end you are less secure even if you don't use any extensions in the first place.