How do I GET RID of Preview?

This has come up before, and has been solved, but the problem has changed. Problem: to open an image file from the desktop, I click on the file, expecting it to open in Photoshop, but, instead, it opens in Preview, which does me no good. The original solution was to do a get-info on the file, assign the "open with" to Photoshop, and then press the "change all" button. I tried that and discovered that my well-established Adobe Photoshop 2018 is no longer available to the get-info window. It's not on the list. So what does it take to make Photoshop available to the system so that I don't have to wrestle with Preview any more? I know, I know, I know, Preview has to be available to the system, blah, blah, so I can't just mince it up and trash it, but now the real alternative is unavailable.