Well, technicaly you can use them as really weird druid ... since no metal armor rule was not applied by Larian.
Or really weird Paladin (once implemented) with REALLY low AC.
![laugh laugh](/images/graemlins/default_dark/laugh.gif)
But it still *technicaly* can be used ...
Bardic items are just for that class specificaly, with no way around (not sure about Adept: Bard feat, if that is even a thing)