After much agony and traversing of rabbit holes, i found a suitable solution using MudBlazor library which contains a 3 state checkbox.

I had tried creating an InputSelect dropdown but the data would not bind to the control. I also considered building my own control which was very much worth learning about, but that is a productivity sump for me. I am not interested in building nuts and bolts. Start with @inherits InputBase<bool?> for those who are interested.

The one drawback of MudBlazor is that it is for blazor and not for traditional asp.net non-spa pages if i understand correctly. But i was already using the former technology without realizing it. recall - i am very much a novice with these ui technologies and razor and blazor can be a blur.