Nowadays it is disputed, whether the youths with only 16 years old should be permitted to get their licence.
Heutzutage ist umstritten, ob Jugendliche schon mit sechzehn ihren Führerschein machen dürfen sollten.
Note the Konjunktiv II on sollen. This is because it's a counterfact. It's at least umstritten. The two-infinitives + sollten construction at the end may sound unintuitive but it's quite common to have such rows of infinitives in German.
There is no passive voice in the dependent clause. That is because sollen introduces a "semantic" passive while being active voice. That whole clause acts as the subject to the main clause which is a semantic passive, too.
Whether the main clause is static passive voice or a coupler phrase is a matter of your preference. I say it's the latter, because no one uses the verb umstreiten in active voice ever. It's streiten um then, and the Partizip II of that one is gestritten um.
Heutzutage wird (darum) gestritten, ob Jugendliche schon mit sechzehn ihren Führerschein machen dürfen sollten.
(Darum is an optional placeholder for the prepositional object. Because streiten takes a prepositional object, and um+Akkusativ is that one. Again, the whole dependendent clause. This sentence also employs a real passive voice.)
So umstritten in the original sentence is just a state assigned to the subject (the whole dependent clause) by the magic of the copula sein. That idea is also useful because of this:
Es bleibt umstritten, ob Jugendliche schon mit sechzehn ihren Führerschein machen dürfen sollten.
See what I did here? The verb bleiben is also a copula. It cannot be static passive voice any more, because that would require the verb sein. But this sentence is meaningful. It says, it's not just disputed now, but it was disputed and keeps being disputed. You may see this as another tense/voice/aspect but German scholars haven't put it into grammar yet. It's just another coupler phrase for now.
→ No passive voice at all.