Another thing @denisvoituron and I are working on (privately, not from Microsoft)...https://try.fluentui-blazor.net. It's still early days, but saving, loading and running snippets, installing NuGet packages works. Everything running locally in your browser by the magic of WebAssembly!
It is based on the same code as Telerik Blazor REPL and MudBlazor Try but modernized and all Fluent UI, of course. Source is not yet available but will be eventually.
Load up https://try.fluentui-blazor.net/snippet/wkGpubOZxReqxWTo and press CTRL+S to see the magic happen!