560
Nearly 500 smartphone brands have left the market since 2017
(www.techspot.com)
This is a most excellent place for technology news and articles.
Not a dig but what makes folding appealing to you? It makes the screen larger at the cost of convenience, while still not making the screen/input good enough for tasks that normally require a computer.
The only good argument I've heard is from an author that loved folding smartphones: it allowed him to write while travelling from and to book signings, so basically it allowed him to work during downtime.