No RAW Imports with LR CLASSIC 5.7.1

I assume it doesnt have the Camera RAW plug in

Actualy the code that is Adobe Camera RAW is in Lightroom. Unlike Photoshop, Lightroom does not use an external plug-in for RAW conversion. Think of Lightroom as ACR wrapped in a nicer GUI running a database (SLQ Lite) and providing a data access management.

just saying.

Application architecture: x64

Good, had it been 32bit you would be up the creek without....

So Adobe alternatives will probably work (for now)

Operating system: Windows 8.1 Home Premium Edition

Not good, Adobe absolutly hates, and disdanes Windows 8, Software has problems running on it. Spending money on a subscription might be a bad experience.

 You might want to go RAW to DNG converter first

Adobe Lightroom Classic MINIMUM system requirements in following link, Be aware that if you have just the minimum, some features may not work, enhanced details comes to mind, GPU acceleration is pickey.

https://helpx.adobe.com/lightroom-classic/system-requirements.html

in that link note:

"**  Not supported on Windows 8.1, Windows 10 versions 1511, 1703, 1709, and 1803."

Alternatives

Download free Adobe DNG converter. Convert RAW to DNG, import DNG into LR 5

https://helpx.adobe.com/photoshop/using/adobe-dng-converter.html

Purchase a third party RAW to DNG converter, like IRIDIENT C- Transformer

https://www.iridientdigital.com/products/ctransformer.html

Abandon Adobe, go to a different post processor program.

For the Canon 6D Mk II, you need at least Lightroom v6.12.

see: https://helpx.adobe.com/camera-raw/kb/camera-raw-plug-supported-cameras.html

As you may know Adobe no longer sells or supports Lightroom v 1 thru 6. Adobe no longer supports perpetual (a.k.a Stand Alone) license versions of their products. And the war over that is lost.

To acquire a version of the product that will open Canon 6D Mk II you would need to subscribe to one of the Adobe plans that include Lightroom Classic v9.1 ( or theoretically Lightroom, as in that cloud app that us old farts have nothing but disdane for)

Be aware, due to Adobe marketing decisions (a.k.a. blunders) (probably to make the millennial smart phone customers happy) the product naming is all fouled up

Lightroom, a desktop app that you place your photos on the cloud, capabilities less than traditional/classic desktop centric Lightroom. IMO exists to make the younger smartphone kids happy, get that market share.

Lightoom Classic, the traditional desktop app in which you store photos on hard drives, the Lightroom you are used to.

Watch out if you look to subscribe to one of the plans. Adobe does offer a plan with just Lightroom, but that is the cloud centric app.

The Photography plan comes in two versions, with 20Gb cloud storage you might not ever use, and a 1TB option. The plan includes Lightroom Classic, Lightroom, Photoshop, Bridge, and a few others

No plan with just Lightroom Classic

Not an Adobe employee, few of us in this community forum are. Try not to  be an Adobe fanboy.