Still chromium at the end of the day. Anything they have control over has the potential to be ruined by them. Don't give them the chance, just fix the problem and use Firefox.
I mean, Vivaldi absorbs whatever changes they like from Chromium, but it's not whole cloth. Vivaldi is specifically not implementing V3 and maintaining compatibility with existing addons.
According to their blog they will stop supporting v2 next year.
"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."
Thats not "will stop", that's "may stop if it becomes unsupportable". Google would have to be activly adding code that fucks with V2 support in order to make it impossible to support it. It's not gone until it's gone.
Meanwhile, in Firefox land, they had no external pressure, and continuously removed features the users wanted, despite outcry from those users.
Is Firefox the better option just because its not Chromium based? That's not clear. What is clear to me is that I don't particularly trust Google OR Mozilla to do the right thing, and (despite using Chromium as a basis for their browser), Vivaldi is doing everything I'd want a dev to do. I wouldn't put it past them to stop taking updates from the main Chromium repo and just start doing their own thing (if Chromium becomes too much of a pain to deal with).
People are complaining that having a mono-browesr is a problem, and I don't disagree, but Google and Mozilla are both assholes that don't listen to their users. Maybe we should be paying more attention to that than which codebase they use.
Mozilla is WAY better than Google. The fact that you're still arguing that a chromium browser is better than Firefox because of a feature you've already been told might not exist next year tells me that i really shouldn't trust your opinion on this. Just use a Firefox fork so you don't have to worry about it, don't give Google control over your stuff because their incentive is to ruin it.
I didn't start using Vivaldi because they support V2, I'm choosing to keep using Vivaldi because of their continued support of it.
I used to use Chrome for testing, but I've dropped it entirely now that ublock doesn't work.
If Vivaldi also drops support for proper ad blocking (I prefer ublock, but Vivaldi has their own blocker that doesn't use any addon framework, not V2 or V3), then I'll go elsewhere, but it sure as hell wouldn't be Firefox unless there was no other option (there are a precious few to even try, but I would try them all before going back to Firefox). And it would probably have to be a fork, in a desperate attempt at some amount of feature longevity.
Also, I don't give Google control over shit. You're making a ton of uninformed assumptions. My browser is a client to access content - nothing more - replaceable on a whim. I don't feel the need to interconnect every software, account, or hardware that comes my way. Those who do are trapped by their laziness and desire for convenience, and almost none of them have any idea what they've given up.