Vivaldi team does not respond to any comments asking about ongoing v2 manifest support; safe to assume it's gone as soon as it's out of Chromium upstream. Given Tetzchner's continual messaging on how important user privacy is to Vivaldi it seems like a strange decision, but I don't know how much effort would be required to maintain the support. They're a small team, so it would be understandable if they would just say it's too hard, but instead they have avoided the topic entirely, which suggests they agree with the direction.