IIRC the only portion of Vivaldi that isn’t open source is their UI code, for what that’s worth. Guess they want to keep an edge there? I’m Currently migrating my Android from Vivaldi to Brave; using xBrowserSync (bookmarks), Proton Pass (passwords), and KDE Connect to keep it synchronized to desktop (debian 13 using KDE Plasma) instead of Vivaldi’s sync. Kind of a pain after using a single service for some time but I don’t trust anyone anymore.