I would like some help choosing my first camera

Hello everyone, I'd love some help in the decision-making process of buying my first camera. I started studying photography recently and I want to buy a camera to practice everything that I'm learning. I want a camera that has a great quality in the realm of portrait photography.

I don't know much about what exactly do I need in the technical aspectsof a camera(Obviously what makes a great photo is a great photographer, but I'm just talking about the technical stuff like dynamic range, sensor size and such)  to achieve a gorgeous looking portrait(with lots of details and sharpness) without going into the Full Frame world.

My budget is somewhere in the price range of a sony a6400 or a canon 80d (which are actually two cameras that I'm considering purchasing right now), and I'm going to use the camera to record videos as well, so that's a factor to consider.

I don't know if I should go with a DSLR or a Mirrorless camera considering the fact that I'm going in the direction of becoming a professional photographer in the future. If there is a professional portrait photographer or an expert that could help me with this decision it would be amazing.

The cameras that I am considering in the moment are the following: Sony a6400, Canon 80D, Canon M50, Canon SL2, Canon SL3, and a Nikon D7100.

Finally, I would like to thank everyone that will be helping me in advance, you're awesome.   

DSLRs have been around for a while, so there's plenty of excellent gear on the used market at greatly reduced prices. Mirrorless cameras are relatively new, so there isn't a lot available used, so you'll probably end up paying the full retail price for your kit. And while there are adapters to mount SLR lenses on Mirrorless bodies, adapters usually present problems  in terms of both image quality and functionality. Lastly, Mirrorless cameras have a much shorter flange focal distance (the distance between the lens mount and the image sensor), so mirrorless lenses must bend light more in order to project an image over the entire sensor, so those lenses are more prone to vignetting, chromatic aberration, distortion, and field curvature (soft corners). That is not to say that those flaws can't be overcome, but in order to overcome them, lenses must use more advanced and more expensive designs. Thus, most mirrorless camera manufacturers opt instead to process images in the camera to "compensate" for some of those image flaws. Unfortunately, that processing often simply replaces one image flaw with another, and worse, there is no compensation for the field curvature, and the compensation for distortion actually makes the corners softer.

When I first was trying to decide on a camera, it was between Canon and Nikon. Honestly it was mostly because they were names I was familiar with. The one thing I wish I knew before I got into photography was that the camera doesn't matter. It really doesn't. If you purchase just about any interchangeable lens camera made after 2010 you're going to be able to get great images. You can even create good photos with a Canon T3i (released in 2011) and a $99 prime lens. 

The real secret is the lens. If you put a crap lens on a $10,000 camera you're going to get a crap image. If you put a $600 lens on a $300 camera you can get some amazing images. When you purchase a camera you are really buying into a lens mount system, and that really is the difference. 

Canon RF Mount: Very new and exciting lenses coming from canon, but they are expensive (at least for now) and the offerings are limited (again, for now). You can adapt Canon EF lenses to RF. 

Canon EF/EF-S Mount: A literal mountain of lenses available for just anything you can think of. The EF-S mount is specifically for the APS-C sensor such as in the Rebel cameras (which can use both EF and EF-S lenses). With the introduction of the RF mount, EF mount lenses are coming down in price, though not quickly because they are still amazing lenses. 

Sony E-Mount: Probably the most adapted mount out there. You can get just about lens to mount to a Sony camera, even Canon EF lenses. There are even websites and Facebook pages dedicated to adapting vintage lenses to Sony camera's. The number of lenses for Sony isn't as large as Canon EF, but you won't be lacking for focal length or coverage and the native Sony G Master lenses are top notch. 

Nikon Z Mount: I personally don't have a lot of experience with Nikon, but Nikon just filed for bankruptcy protection. If they survive (I am sure they will) they have been used by professionals for decades. I have always compared Nikon to Volvo. I don't know anyone who drives a Volvo, but the people who do drive them seem to love them. It is just not a system I have any real experience with. 

The two camera's you are considering are great camera's that will serve you for many years. Regardless of which you chose, you are making a good decision with either of those.