Does QB Desktop use Dot Net?

Hello there, @ToddAndMargo. I'd be happy to answer your query.

Yes, Quickbooks Desktop (QBDT) 2021-R10P use Dot Net. And it's all available on all versions of QBDT.

To better guide you on which versions of Windows 10 are compatible with your QBDT account, I recommend checking this article: Which Windows 10 version works best for QuickBooks Desktop?. It also contains information on how you can sure you're on a version Microsoft currently supports.

Additionally, you may want to check out this link in case you need to know more about the features included in the QBDT 2021 release and how you can use them to benefit your business: What's new in QuickBooks Desktop 2021. 

Let me know if you have other questions. I'm glad to help. Take care always.