Vivaldi? Killed, Chrome clone. Edge? Killed, Chrome clone. Brave? Killed, Chrome clone. Firefox? Technically a separate engine and in theory among the last hopes, but so sclerotic it follows Chrome in almost all of its decisions. (Can MV2 be kept as a stable basic-security-maintenance-only API? Probably not) Safari? Can be gone around on desktop (my grandparents use Chrome because of Google prompts), has a stranglehold on mobile, but that has its own problems, and likely once users can ~sideload~ install software (potentially from other app stores), there will be a Chrome surge on mobile, forcing manifest V3 over there too, and the ad trackers will win the war.
Or maybe they already have? More likely, I personally am tiring of the cat and mouse game between the spyware makers and devs that fight for the users.
[1] UPDATE: https://blog.mozilla.org/addons/2022/05/18/manifest-v3-in-fi... PREVIOUSLY: https://blog.mozilla.org/addons/2022/06/08/manifest-v3-firef...
* In the sense that one browser implementation, and not W3C or WHATWG web standards, drives the web browser market. Chrome is much more evergreen than IE.