Not really, among "normal" banks. This does seem to be the case with the new "challenger" banks like Monzo and Starling, which are all "mobile first" and are basically impossible to use if you don't have an Android/iPhone. But every regular bank in the UK has a website with online banking, often with more functionality than the apps, but maybe this is different in other countries - online banking in the UK has been commonplace since before mobile apps were really a thing.