Is it permissible to seek divorce from a husband who is excessively lazy, a bad role model, and neglects his prayers, knowing that he is of good character? And is seeking divorce in this case considered a sin?

If what was mentioned about the husband's actions is proven, he is indeed wrong in them, especially neglecting prayer, which is a great sin. The wife has done well by being patient and advising him, and she will be rewarded for that. She should continue to advise him and pray for him frequently, and seek help from some righteous individuals among his family or friends if necessary. It is not permissible for a woman to seek divorce except for a legitimate reason.