Well, as long as their eligibility/registration isn’t tossed under dubious means, there are enough polling stations where they live, they have the ability to go (as in not working or their work allows them to go), their vote sent by mail isn’t caught in a USPS black hole until right after the deadline despite being submitted long before, so on, and so on.
A dumb phone and a feature phone are not the same thing, and a feature phone may connect to the internet.