I'm not aware of a standard answer to that one.
I'd say it's either:
1. An adverbial, so you could paraphrase as "independently..." though that sounds like it has a slightly different sense to me.
or
2. An appositive, meaning a "renaming" of some earlier element, perhaps the predicate "They are often [used....] [and] [independent...]" or maybe extending the kind of discrimination, maybe displaced to the end of the sentence because it's long.
I feel like it's probably an adverbial rather than an appositive, but the structure is a little odd.