Fertility Awareness can be learned and practiced by anyone who cycles (or has the capacity to cycle). It’s not true that you need to be in a committed monogamous relationship, or identify as a woman, or have sex with men. In fact you don’t even need to be sexually active. I’ve worked with couples waiting till marriage to have sex, people involved in polyamorous relationships, and women in relationship with other women who want to have a baby.
Maybe people think that Fertility Awareness is only suitable for women in committed, monogamous relationships because you don’t have to use condoms if you practice Fertility Awareness. But prevention of sexually transmitted diseases is a separate consideration from contraception. If you need to use condoms (female or male, with or without HIV PrEP), use them, regardless of what kind of relationship you’re in. Even if you’re not heterosexually active, you can still benefit from an understanding of Fertility Awareness, for insight into your health and to be more empowered around your sexuality and reproductive health care.