I would still use the framework that I have always used F# Giraffe/Suave. I know that logically it seems to make sense on paper to use the same language on the server as the client but I just don’t see the value proposition in practice. You can develop F# mobile apps with Xamarin but I still prefer Swift.
Since server programming is nothing like programming for the device I just don’t see the advantage. I have seen posts where people bring up that you can use models on both, but unless you type 5 words a minute that doesn’t really buy you anything. You won’t really be sharing anything of value between the client and the server since the problems you solve are very different.
At the end of the day I think the only advantage of having the same language on both is that you like the language and enjoy programming both on the client and server. And developer happiness is not something to be taken lightly, but I don’t see any real business value in it. Languages are so easy to learn with all the information out there, that using a single language just isn’t something that I would consider in a business context, only a hobby one.