Photos, both RAW and JPEG, appear darker after import in both LR Classic and regular

I have a similar issue- I upload to my computer and it chages my photos all to be under exposed grealty and looks completely differnt than what my camera is telling me. Ever find a solution? 

Thumbnails you see in the import screen are not converted previews, be they JPEG or RAW, especially RAW. The thumbnails of the RAW files are actually embedded JPEG files contained within the RAW files. These are small JPEG images created by your camera, they allow you to view the RAW info in camera, you are not actually seeing the RAW data. Historically theses embedded JPEG files are very small, newer cameras have improved on that. As such these thumbnails are not great for viewing.

LrC creates, eventually several preview files for viewing in the Library module, standard, 1:1, etc, things will not look great until they are created

The File explorer cannot display raw files, so it displays the embedded jpg preview, which may contain settings from the camera. These settings are ignored by Lightroom when it renders the raw files, it doesn't understand them.

Furthermore, the File explorer is not color managed, and will not display correct colors in any case.

You also posted screenshots from the Import dialog (please use the Insert Photos button in the toolbar to insert screenshots directly in your posts), and because the images have not been rendered yet, it displays the embedded jpg previews, and unlike the rest of Lightroom, it is not color managed.

Your screenshot from Library (which I inserted below) shows that LR is in the process of building previews, and it's not clear whether it yet has rendered its own thumbnails, or still is displaying the embedded previews, which will appear initially.

The reason that images appear darker in LR is probably because of some camera setting that brightens the image, which LR doesn't understand and ignores. I suggest that you turn off/neutralize any such camera settings – Picture styles, or whatever Canon calls them.

You can also check if Adobe has camera matching profiles for your camera that you can use as a preset, which will mimic picture styles applied by the camera. Go to Preferences > Presets to find out.

See also https://helpx.adobe.com/lightroom-classic/help/raw-defaults.html

You say you 'preview them in a folder" but that doesn't imply however they are viewed is color managed. So that's one possible issue. 

You can't 'preview' a raw outside of ACR/LR and ever expect a visual match because raw has to be rendered using the ACR engine which is proprietary like all raw converters. You may be viewing an embedded JPEG, where that preview was built elsewhere and differently (than LR/ACR). So you can't expect a match. 

At least with raws, what you see in LR IS correct based on its initial (current) instructions to show you that preview.