While it'd be difficult, you can usually make do with a browser or visiting in-person (e.g. with a bank, they need to know who you are anyway, so visiting in-person is mostly just an inconvenience). Physical ID is likely still going to be a thing for the forseeable future since at minimum there are bunch of old people who basically don't know how to use smartphones (or at least use them well).
Messaging is more problematic. You could probably use a combination of something that functions on your computer and a dumb phone for urgent things (although since texts/calls wouldn't be E2EE, you'd have to assume the govt knows the contents of the convo).
IMO it's entirely feasible just quite inconvenient.
I personally don't think that's really feasible unless they provide smartphones for every citizen themselves, and even then people like my grandparents would basically not be able to live given that they only barely know how to message me (and even that they do wrong sometimes, so...). They can certainly make it difficult without a smartphone, but they likely can't completely eliminate physical IDs until those issues are gone.
EDIT: also, if that does become an issue at some point, you can keep your smartphone off unless necessary and don't use a simcard. When on keep it in airplane mode. If you need a connection to use digital ID, do it briefly over wifi (since presumably most places you'd need digital ID would have wifi) and then turn it back off. While not perfect, this would probably be good enough for most people.