Intergender may refer to a gender that is in between male and female specifically, or a gender related to being intersex.
Ultergender is a gender modality for “trans intersex” people. It describes intersex people who identify as a gender other than their assigned gender at birth, but do not feel the term “transgender” describes them, due to being intersex.
Ipsogender is a gender modality for “cis intersex” individuals. It refers to intersex individuals who identify with the gender assigned to them at birth- either because they were coercively assigned a gender, or because it was not known they were intersex until later in life, making them “cis”. However, they recognize that cis-ness does not apply to intersex individuals in the same ways it applies to perisex individuals, and so a cis intersex idividual may identify with ipsogender to underline the fact that they are not empowered by or protected under cissexism.