I had always thought that Johhny Cash played a jumbo Gibson guitar as his main instrument, and there are a number of pics with him playing a flame topped model of the same. I noticed though that there are plenty of pictures of Cash playing Martin D28 syled guitars, including one here:

https://www.rollingstone.com/music/music-country/johnny-cashs-at-folsom-prison-at-50-an-oral-history-629871/

Google Images includes a variety of different guitars that Cash seemed to have used.

https://www.google.com/search?sca_esv=aa355e4347ca4578&sxsrf=AE3TifNvAtobc6CV5Fh7udd9TvHFGLkBFA:1753226562509&q=johnny+cash+guitar&udm=2&fbs=AIIjpHxU7SXXniUZfeShr2fp4giZ1Y6MJ25_tmWITc7uy4KIeiAkWG4OlBE2zyCTMjPbGmPgfe_7ak8LUsonpWCvT6w67NYoMQ3FpL7X1X-2E-QRutwC_koOFlshCmbWIdGMUNc5JYD677jV4g1vfbazEfXFmGbpO4Ot6DT-FsUzgatdGwBD_wXT_hw4aBW6ISn9eI70UALgY44qvPYV39yQw_ChE4Syjw&sa=X&ved=2ahUKEwimn-DzzdGOAxX-KUQIHQ2qMMkQtKgLKAF6BAguEAE&biw=1082&bih=434&dpr=1.25

Lest we forget - before he became megastar, Cash frequently performed with at most one supporting guitarist (or none at times) and a bass player.

A quick YouTube search has Cash on the opening number of Hootenanny at the U of Florida: