Tolkien is a bit flakey and extremely vague on this himself. The show only maintains adaptorial rights to the LoTR appendices (presumably), and all they say of this is "Tar-Palantir attempted to amend the evil; but it was too late, and there was rebellion and strife in Numenor. When he died, his nephew, leader of the rebellion, seized the sceptre, and became King Ar-Pharazon." That's it. Miriel barely features even the briefest of mentions in the appendices.
The Silmarillion goes into more detail, with Palantir's brother taking leadership of the King's Men and working against him, but there's no explicit mention of a full rebellion. Tar-Palantir grew "darkened with grief" and indeed spent most of his time secluded in a tower until he died.
Based on this, the show hasn't completely broken from the books yet, but given Tar-Miriel is shown dressed for battle amongst soldiers in promo material, she's clearly getting the girl power treatment. It would be funny if they fully role-swap her with Ar-Pharazon, letting her bring Sauron to heel only to set up the complete destruction of Numenor. That would sure be a feather in the cap of feminism.