That’s how it works for now, but eventually the code itself will be removed from chromium, not just disabled. At that point they’d have to maintain a large patch set reimplementing it, which would be extremely time intensive to maintain and keep secure.
I know, precisely. But it is an alternative without this nonsense, kinda the only one. And the only option to actually stop the Google monopoly that led to this.
They are not exactly forks. They still get the upstream chromium changes into their code base. So they will all lose manifest v2 when the core disappears from chromium.
They are more like downstream branches. It is possible they will do the gymnastics to keep manifest v2 but it's not guaranteed