@maleandroids @selzero @schmidt Well, at least as of a few months ago, it wasn't clear to what extent Vivaldi could maintain support: https://www.reddit.com/r/vivaldibrowser/comments/x9ttji/vivaldi_and_manifest_v3/
(The underlying issue is that support for the APIs which uBlock Origin uses is being dropped from Chrome's "engine"; it may be difficult for Vivaldi to retain it. And the extension will be dropped from the Chrome store regardless. uBlock Origin will release a version that tries to work with Chrome's newer APIs, but probably work worse.)