If it's appropriate I might commiserate with shared experiences through the lens of my own autism, and share resources if it's something they're already thinking about. If it's not something they're thinking about, it's not on me to press it.
For me this has to do with the importance of framing autism as an internal state versus some slate of nonstandard behaviours as seen from outside.
I'm open about my challenges and interests. Over the past few years most of my 20+yr friendships have mentioned to me without prompting that they are autistic or exploring autism. I talk about it and when people are ready to talk about it, they talk to me. I have so many bookmarks to share.
My mom told me I was autistic when I was 8, but I know I wasn't diagnosed, and I didn't get that understanding myself until I was 40. Maybe sitting me down in front of Rain Man wasn't the right way for her to have that conversation, but if she were alive she is the one that yes, I would tell her she's autistic.