ADHD without treatment

I have a partner who is diagnosed (but he knew beforehand) with ADHD. Prior to being diagnosed he was my first boyfriend many years ago, now we are back together since march. Since this is not that long yet I am assuming that I am currently still experiencing the hyperfocus, I know I will be devastated when that will end.. but I know it will come.

Anyhow; I am reading the book ADHD relationships by Melissa and Dr. Ned and they often write about medical treatment. We sometimes talk about ADHD and I know he once said that he has used medication earlier, but he stopped using that because he didn't like the effect it had on him. I understand that because I had the same feeling about anti-depressants many years ago.. it stopped all of my feelings like I was living in a bubble, what he says is pretty similar to that.

So my question is: is it possible to not medically treat the ADHD and still have a thriving relationship, specifically after the hyperfocus ends? Any tips?

I'm only in the second chapter, so I am hoping that the focus will be more on tips instead of the medical treatment.