Dumb mobile phones still have SMS, so 2FA still works and since it is a telephone, talking to friends and family is also possible.
I suspect the reasons the OP gave up on the smart phone was to get away from all of those phone apps.
Unless their financial institution offers a non-smartphone 2FA option, such as a PIN-based card reader[0], having to use SMS-based 2FA is a reasonable price to pay.
[0] https://en.wikipedia.org/wiki/Chip_Authentication_Program