FWIW, as of 2023, [Preview no longer supports postscript files](https://support.apple.com/en-us/HT213250). Which is pretty annoying if you like to hand write postscript.

From that Apple note, a nice to know is that you can directly drag a ".ps" file on to the printer queue and it will be printed (assuming your printer talks postscript!):

> If your printer supports PostScript, you can continue to print .ps and .eps files by dragging them into your printer queue: select your printer in Printers & Scanners settings, click the Printer Queue button, then drag the file into the printer queue window to print it.

To let me view a .ps in macOS I’ve installed the ghostscript suite, which includes tools to convert .ps files to pdf files. There're options for installing at [Installing Ghostscript on Mac OS X](https://wiki.scribus.net/canvas/Installation_and_Configuration_of_Ghostscript#Installing_Ghostscript_on_Mac_OS_X). 

I took the brew option: `brew install ghostscript`. 

There's no "ghostscript" app or command installed, but you get a whole bunch of tools, and one is `ps2pdf` that will take your ".ps" file as an argument and write a similarly named ".pdf".