If they're a clamshell style with a physical keyboard, as with the Psion Series 5, possibly:

<https://en.wikipedia.org/wiki/Psion_Series_5>

Folding-screen phones are an expensive gimmick, with inevitable exceedingly expensive repairs:

<https://arstechnica.com/gadgets/2023/09/the-pixel-folds-scre...>

I predict a flop along the lines of 3DTV.