Also, of note regarding the Photon S (or Upgraded Photon), depending on what firmware version, you may or may not be able to use files with the .Photon extension straight from Chitubox. The latest firmware update for them supports both .photon and .pws (the new Anycubic "proprietary" format), but some of the older one can only read .PWS format, and Chitubox can only slice as a .PHOTON.
However, if you prefer Chitubox over the Anycubic Photon Workshop software (which is essentially a skin of Chitbubox with a few streamlined options added) all you have to do is use Save As... to save your supported file in Chitbox as an .stl file, open that .stl file in Photon Workshop, and just hit the slice button to slice as a PWS file
Although the latest version of Photon Workshop is actually pretty good in it's own right, especially for beginners, and you may not even find the need to use Chitubox unless you want a bit more manual control. There are also some features of it that I think are better than Chitubox and sometimes I find myself doing things in both.
Yeah funny you should mention the Chitubox as I was watching a video of a guy saying he uses Chitubox to add the supports and then exports it back to Photon Workshop for the final print - his explanation being Chitubox is just better for that purpose than Photon.