Yes, although iOS betas (and even recent full-release iOS 11) can (and often do) break external DAC functionality from iDevices, there are plenty of people successfully using iOS 11 with Mojo and other external DACs, in recent weeks.
On the other hand, there are numerous examples (not just in this thread) of genuine Apple CCKs becoming faulty, with all sorts of confusion, disbelief, misappropriated blame to other devices, etc. etc., only for people to eventually realise that,
yes, genuine Apple CCKs really do sometimes develop faults.
In short, since iOS 11 is currently working well for many people with external DACs, your first port of call should be to an Apple store, to try a new CCK.
I hope this works for you (I suspect it will), and please let us know how you get on, either way!