I directly copy your example code from: https://demos.telerik.com/blazor-ui/grid/editing-incell into a server-side Blazor page using .Net Core 3 preview 5. Telerik UI for Blazor 0.5.0.

I run the app and the grid works perfectly apart from the "Add Employee" button. When I click it, it does nothing. No new blank row is added. Please note that the other grid command buttons work fine including "Delete" and "Edit".

The first official 1.0.0 version brought some changes in the command names, and the documentation is for the latest version (which is 1.1.0 at the time of writing, and I strongly advise that you upgrade to it). 

You can find the old command names in the following KB article: https://docs.telerik.com/blazor-ui/knowledge-base/grid-update-from-0-5-to-1-0. 

The demos also run on the latest version and thus their code would no longer work on the 0.5.0 pre-release version.

Wow! I had no idea 1.1.0 had been released. For some reason the private NuGet feed I setup as per https://docs.telerik.com/blazor-ui/installation/nuget is still showing 0.5.0 as the only available version.

I downloaded the .zip archive from my "Downloads" page and the "Add" button now works. So thank you for that!

However it would be great to hear any tips on why my private nuget feed is still just showing 0.5.0...

Yes, that does seem to have fixed it.

Is there another source (like a blog or webpage) I can manually watch to ensure I learn about new versions, just in case the nuget feed again doesn't update for me for some reason?

We tend to publish blogs for new releases, and the release notes list will show a new version: https://www.telerik.com/support/whats-new/blazor-ui/release-history.