Consider:

The Faithful of Númenor having clandestine "schools" of their own, their children gathering in their houses to be taught the forbidden elvish tongues, and more importantly, unexpunged history and religion (although I do feel slightly hesitant to use the latter word in relation to the Legendarium). Definitely most prominent in Andustar and later among those deported from it, often, these lessons masquerade as trade schools, so that whenever the king's soldiers are at the door, one can quickly hide the books, bring out embroidery hoops and spread cloth over the parchment.

Illicit theatre performances! Ask me about my headcanon that Númenor invented theatre one day, but the gist of it is that culturally, it's pretty important, but at some point a very stringent censorship becomes the norm, and many erstwhile classics are forbidden (not to mention any new plays with a Faithful message). Cue the practice of semi-professionnal troupes secretly performing in people's courtyards with very little in terms of scenography/costumes, but with a strong emphasis on good acting. Theatre is not considered a low occupation in Númenor, so even certain relatives of the Lords of Andunie take part in those shows.