This is a thing - shipping sometime in November of this year

Open source too.  $400 - from here: Sky's Edge:

The Rotary Un-Smartphone is a followup to this personal project. It's a production-ready ground-up design with all new parts (yes, the rotary dial too) and many neat bells and whistles.

• • Pocket-sized
  • Full LTE connectivity. Obsolescence-proof for at least another decade.
  • Access and call your personal contacts faster than with a smartphone
  • Use your own SIM card with your favorite carrier's "Bring Your Own Device" option
  • Real (mechanical) ringer bell made gold or silver-coated brass; externally visible
  • Receive basic SMS messages and send pre-typed messages and numeric strings
  • 2 displays: Front-side OLED and back-side ePaper
  • Physical disconnect switch for the microphone
  • Mechanical power switch
  • MicroSD card stores contacts list as a text file
  • TRRS headset jack
  • USB-C charging port
  • Incandescent-like indicator LEDs
  • Weighs 163g [6oz]
  • Injection molded parts available in several striking colors

Halfway tempted.  Great fun to pull it out to receive a call...