My open source rotary cell phone went viral (surprisingly, to me and my husband), and people seem to be interested in it. The original description with links...
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 (11.0cm x 7.5cm x 3.0cm)
Light-weight (163g [6oz])
Full LTE connectivity. Obsolescence-proof for at least another decade.
Access and call your personal contacts perhapsfaster 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 for caller-ID and dial entry, and back-side ePaper for contacts display
Some info from the r/cassettefuturism post:
Rotary Un-Smartphone by Justine Haupt (real product)