@brendanhsweeney In order for Google to offer suggestions, a "suggest" URL has to be filled in by the user (easy, and easily come by, but not legal for Vivaldi to ship with due to restrictions placed by Google).
Full editing of search engines can still only be done on desktop, but it will sync with mobile.
What sometimes happens is, a user will make a change to a search engine (like filling in a suggest URL) and a later Vivaldi update will not see the search engine as being installed, and will add an instance of that search engine. So now you have two Google (or whatever) search instances. If you remove the new one you can reinstate the old one as default, and all returns to normal.
This does not always happen and, over time, Vivaldi devs have tweaked the update code so that the instances where it does happen have been narrowed down. Sorry this happened to you.