I remember from the late '70s and my lesbian friends then, that "wimmin" was another popular alternative. The idea of course was to bypass the linguistic implication that woman and women are subcategories of man and men.
Spelling it womyn or wimmin isn't and wasn't the problem, it was identifying physical gender as the source of our societal "masculinity" problems.
That both interferes with recognizing men as its other victims, and promotes "gendered" exclusion.