You can swap the whey protein for another protein powder, but textures will vary. Plant-based powders usually absorb more liquid, so add an extra splash of milk if needed.
If you don’t use protein powder, replace it with extra oats or plain flour and add a little more sweetener to taste, you may also want to add a tsp of vanilla extract. The pancakes will still work but won’t be as high in protein. Any milk works here, and Greek yoghurt can be swapped for skyr or a thick dairy-free yoghurt if needed. You can also swap oats for plain flour if you prefer.