Perhaps it's a story where the husband has been hiding his adventurous spirit or a very romantic side. In the novel, the wife might start to notice little things that gradually show her this new, exciting side of her husband. For example, he could secretly be writing beautiful poetry or be involved in some thrilling hobby that makes him seem more appealing.
Since it's called 'My Secretly Hot Husband', the main characters are likely the wife and the husband. There may also be some secondary characters like friends or family members who play a role in the story, perhaps by either helping or hindering the wife's discovery of her husband's 'hot' qualities.
We have no way of knowing the specifics of the situation where her husband secretly bought a new phone for his own use. Therefore, I am unable to answer this question.
You might consider giving him some space to explore the manga on his own and then discussing it together. Sharing your enthusiasm and showing how it brings you joy could potentially get him on your side.