I put dryfiring in two groups.
Dryfiring (for training) and dryfiring (snapping) for storage or most commonly when you run out of ammo...
Everyone who shoots .22 repeaters will or has snapped on an empty chamber. Very few lock open when empty, so its a very common thing and should not damage the gun. Many of the more modern designs are made so that the firing pin will not hit the barrel with nothing in the chamber. Many, NOT all.
Dryfiring for training is a different animal. Snapping with nothing in the chamber once in a while is one thing, doing it hundreds to thousands of time, or tens of thousands of times is something else again.
Fired cases are "free". Drywall anchors are cheap. Actual snap caps aren't terribly expensive. If the maker says its ok to dryfire, then its ok to dryfire. If not, its not. it's really that simple.
If you don't KNOW, assume its not ok.
And always assume its a bad idea on anything made pre-WWII. Just in case.
And, be aware that even on guns where the firing pin does not hit the barrel when snapped empty, SOMETHING is stopping the firing pin. Most of the time, that means a steel on steel impact. With nothing cushioning it, the firing pin striking steel CAN (and has) become damaged or broken.
Not always the tip, some pins have broken "further back" due to the metal crystalizing and becoming brittle from repeated steel on steel impacts.
Particularly vulnerable to this are older designs.
If you are going to deliberately snap for practice, I feel not using something as a snap cap is negligence. Some might even consider it abuse. Your gun, your $, your call...