Huh? But you can use C# on a Mac... I should know, I just came home from doing that all day at work. .NET Core works great on Mac, and imports many dlls just fine.
That being said if it was quite an old dll, and never compiled under PCL or netstandard, maybe not. There's still Mono, but, well, I can definitely understand reluctance in this case, and indeed would choose a different way in a different language myself, if that was my only option left that way.
if i remember correctly the DLL was responsible for the library to not be portable. It might be that i don't remember this correctly, but some crucial part was not available so i could not use it.
That being said if it was quite an old dll, and never compiled under PCL or netstandard, maybe not. There's still Mono, but, well, I can definitely understand reluctance in this case, and indeed would choose a different way in a different language myself, if that was my only option left that way.