Merchant - you can buy a brand new (albeit, basic) smartphone nowadays for under £50. Buying one to cover yourself for a vaccine passport need not be particularly expensive. By way of comparison, Trailfinders in west London charge £75 for a yellow fever vaccination (single dose)
Perhaps time to give a smartphone a go and see how you get on with it ? Talk to a friend who can show you the basics, and take your time finding your way around how to use it - maybe also get a friend to download a few apps on it that match your interests. You might find that they're more useful than you think.
Regarding battery issues, most smartphones will last a few hours with constant use (i.e. surfing the Internet on it) or a couple of days if used very lightly. If you carry a charger with you, it's usually possible to find a spare socket at an airport. Some airlines have sockets for phones at each seat as well. As long as you charge your phone fully before leaving home, you are unlikely to have any difficulty with the phone being unable to retrieve a boarding card / vaccine passport. I imagine that on a really long haul flight, you could maybe charge the phone at your seat mid-flight, or if desperate, find a socket at the arrival airport before immigration.
That said, I have downloaded a boarding card to my phone and found the battery ran out of charge before I could board the plane - I've found that if asked nicely, checkin desk staff (even for Ryanair) are always willing to reprint a boarding card for you for free once they see on their system that you've already checked in online
Last edited by davidjohnson6; 14th Mar 2021 at 00:22.