So I’m pretty sure I’m polyamorous but my mom is completely against polyamory (it came up because my friend and his boyfriend are moving in with their boyfriend).
Your mom’s opinions and reality do not have to be your opinions and reality. It is okay to do or be something that other people don’t approve of.
If there is an issue of safety - if you still live with your mom and feel that she would act in a way that threatens your well-being, security, or relationships - then it is okay to stay closeted and wait it out.
But it’s not your job to convince your mom that polyamory is healthy and acceptable. Changing her mind is not a prerequisite to you living a healthy, happy life and having fulfilling polyamorous relationships.
I have family members who disapprove of my polyamory. I have people in my life who disapprove of my career choices, my diet, my hairstyle, whatever. There are a frighteningly large number of people in my country who disapprove of my beliefs and my personal right to exist. That means I need to take steps to protect myself, emotionally, physically, financially, etc. but it doesn’t mean I cannot or should not be my real, best self.
Some other posts about this: