lld has parallelism here and there, as well as ld64. I do believe ld64 is technically the first linker that started parsing object files in parallel.
Parallel linking was conjectured impossible for a while without breaking static archive semantics (AB-BA problem). Michael has a good explanation in https://www.youtube.com/watch?v=ONGVraXbJOo (minute 3 and beyond).
Before LLD?