Im pretty sure Fresh is still actively being maintained as it has its own full time maintainer
About using shadcn with Fresh, yeah seems like theres not really an easy way to make it work
React/Nextjs are heavily optimized for Node.Js ecosystem so theres really not much benefits of using Deno with it.
You can try, but you’ll just end up using npm: specifiers all around your app. Thats also the reason why Deno has Fresh as its own web framework