The Musgrave Texture isn’t really gone, but just incorporated into the Noise Texture Node, as @tatasarts has already figured out.
You can use a conversion, if you want to match numbers from a tutorial, but I recommend just using your eyes to get the result you want.
The default Musgrave translates in 4.1 to a Noise Texture with a Roughness of 0.250 and a Detail of 1.000.
Increasing the Dimension to 4.000, would mean decreasing the Roughness of the Noise to 0.0625.
In fact, let’s get this over with and give a formula for the conversion. This is what I came up with:
Musgrave with a Detail of d, a Dimension of m and a Lacunarity of l converts to a
Noise with a Detail of (d – 1) and a Roughness of 1/(l^m) (and a Lacunarity of l, obviously).
