Nequent refers to genders, gender identities, sexual/romantic/tertiary orientations, sexes, relationship categories, and other related things which are neither LGBTQ+ nor conformant. This means they are not LGBTQ+, but they are also not the "standard" for their category.
There are many clear-cut standards for what gender, gender identity, sex, orientation, and relationships are "supposed" to be in society, and for many of those categories, not meeting that standard would make one LGBTQ+, but there is nuance to everything which means some identities are neither LGBTQ+ nor conformant.
The most common reason for terms falling into the nequent category/criteria is that they fit into a category that is either too new or not well known enough to have a "standard" for it. For example, the idea of tertiary attraction has only recently begun to be more explored among variant communities, so there's no societal "standard" for things like tertiary attractions (sensual, queeplatonic, etc.), meaning using those terms isn't conformant because there's no existing standard for those terms to conform to, but they're also not LGBTQ+ because they also technically don't break any standard- there's no standard for them, so they neither live up to nor break a standard, making them neither conformant (living up to a societal standard) nor LGBTQ+ (not living up to the societal standard).