Simpler to just buy the download version from the Adobe website. No reason for a DVD. That way if you need to re-download you just go to their site.
The stand alone version is here:
https://creative.adobe.com/products/download/lightroom You do have to sign up for an Adobe ID. This is the free trial, once you have it up and running just buy a license.
The subscription model has a lot of people hating on it, but I've found it to be a bargain if you use Photoshop. If all you want / need is Lightroom then the standalone version is fine. Just be aware you will not get interim feature updates like the subscription version.