I feel like, in a day to day sense, my phone is more useful for chat and email than phoning people. I think a minimum phone that suited me would be closer to a pager.
The ideal smart phone for me would be an old BlackBerry.. physical keyboard and everything
I need my phone to write and read Signal / Matrix messages and to use MFA. Unfortunately, dumb phones are generally too dumb for these requirements.
Perhaps an iq100 phone? Punkt is kinda close.