CANON M50 + Vitrox booster + Canon f2.8 MACRO 100mm

You have exposure simulation turned on.

Canon lenses are ALWAYS set to the max aperture the lens can support when composing whether you are using DSLR or Mirrorless.

This is to give you as much light as possible when viewing the scene.

When you take the shot, the lens stops down to F22 whatever and then the shutter release happens.

Now, DSLR can't do this (except in live view), but mirrorless CAN - Exp Simulaton shows you a SIMULATION of what the exposure will look like at that shutter speed and aperture.

While this is generally an amazing mirrorless feature - In some environments, this is a disadvantage.

Consider a studio environment. You up your shutter speed and close down your aperture until it is completely dark, this is called killing the ambient, the idea is that when you fire your studio lights, your exposure will be correct - the problem is, that your camera shows you a simulation of the ambient light at that exact moment - so you have a pitch black screen.

Exposure simulation in this situation is literally showing you that your scene will be well underexposed. At f22 and ISO 200, pretty much anything other than being on the surface of the sun is likely to be a bit dark

Kick your ISO up, open your aperture, lower your shutter speed or add in external light - all of these will work. As you are doing macro, you probably want to add external light or use a slow shutter from tripod - depending on what you are photographing.