I have read some articles about DSLR and mirrorless cameras, and one thing all people insist on is that:
DSLRs use the same design as the 35mm film cameras from the past. A mirror inside the camera body reflects the light coming in through the lens up to a prism, and into the viewfinder for you to preview your shot.
But I have also seen that we can preview photos on the Canon M50, for example, which is a mirrorless camera. Here a photo of the Canon M50 with the previewer at the top of the device: https://www.imaging-resource.com/PRODS/canon-eos-m50/Z-M50-BACK.JPG
So what it is the point, when it seems also mirrorless camera also allows one to preview photo using a kind of lens, like a classic camera?
My question is slightly different to the possible duplicate proposals because I assume that this is the same thing, the other question already know it is a different thing, so my question begins from different assumptions, hence difference emphasizing in the answers. That said the two questions are complementaries I think, once you know why it's different you can dive in the advantage of one or another.