How to custom Switch to bind value as string "Y" and "N" instead of bool ture/false?

Better approach will be to exerted your data model with additional boolean property that will get/set the original string property. Check this article for more info:

Thanks for extending model with additional property advice.

What if to custom radio button list?
Since we have common baseline to use https://blazor.radzen.com/ components to complete mentioned project. They want to have Switch for their Y/N data, just like phone app settings, even browsers settings everywhere nowadays.

My first proposal was traditional Y/N dropdown list, but they want to have a clear visual effect.

Not sure I understand the problem. If your data are strings you can use additional properties to wrap them in boolean or whatever type - for example integer foe radio button list values

I prefer to have a component like Switch can bind value with "Y" and "N" directly.
For some other cases, some component like Switch can bind value with 1 and 0 directly is desirable.

I’m afraid that we don’t have such component.

Noted, thanks for understanding!