Usage of C# packages from F# is simple and without issues. The other way is a bit more clunky, but frankly, you will not want to write any C# once you are on the F# side.

I have been programming in F# full time for the past 7 years and I hope that rumours of its death are greatly exaggerated. Perhaps this comes from a point of view that if something is not growing 10x each year is dead?

It's not a JavaScript framework that has an average lifespan of a couple of years. It's a fully featured, complete, very productive language that makes programmers life easier and more enjoyable.

I wonder how much of the "death reports" are also just that F# is one of Microsoft's original successful invites for open source community contribution. It was so successful that some months the majority of Github contributions to F# come from outside of Microsoft and that can appear "dead" for "Microsoft officially supports this" rather than a sign that the project is healthy and seeing a lot of community love.

F# and C# packages are compatible.