Update November 23. Mesh hair can no longer be converted into particle hair during import. Use the Make Hair tool to expliticly make the conversion afterwards. See this post for details.
Here is the Hair section of the Global Settings dialog.
We notice that the Strands As Hair option is gone. It is replaced by the Strand Type option, which can take on three different values: Mesh, Line, and Hair. These control how strand-based and polyline hair are imported.
The Advanced Setup > Hair > Make Hair tool also offers new ways to convert mesh hair into particle hair, reusing the code used to import hair. The dialog displayed by the Make Hair button has a new line below Hair Color, which specifies the type of strands in the mesh hair. Depending on the type chosen, different algorithms are applied to create particle hair.
As always, we must delete any hair cap before creating particle hair, or separate it from the hair mesh.
particle hair does not.
We could illustrate this with strand-based hair imported with Strand Type = Mesh, but tube-shaped strands can also appear in other assets, such as the hairstyle above. Meshes with many tubes could not be converted to particle hair before.