Arc
defaults write company.thebrowser.Browser.plist ExtensionManifestV2Availability -int 2
Chrome
defaults write com.google.Chrome.plist ExtensionManifestV2Availability -int 2
Chrome Beta
defaults write com.google.Chrome.beta.plist ExtensionManifestV2Availability -int 2
Chrome Dev
defaults write com.google.Chrome.dev.plist ExtensionManifestV2Availability -int 2
Brave
defaults write com.brave.Browser.plist ExtensionManifestV2Availability -int 2
Brave Beta
defaults write com.brave.Browser.beta.plist ExtensionManifestV2Availability -int 2
Edge
defaults write com.microsoft.Edge.plist ExtensionManifestV2Availability -int 2
Edge Beta
defaults write com.microsoft.Edge.Beta.plist ExtensionManifestV2Availability -int 2
Vivaldi
defaults write com.vivaldi.Vivaldi.plist ExtensionManifestV2Availability -int 2
This appears to not work anymore ahead of the June enforcement. Tried with Arc without success.