Memes and online culture count. Just like writing counted as culture when that tech emerged. There is an online bi culture, ime. It’s laid-back, self-aware, and flexible. And it sits in chairs like Riker from Star Trek: TNG.

But “affirming your bisexuality” is different for everyone. Due to gender norms, women wearing bi pride flag colors are less likely to be assumed to be queer, as misogyny means “feminine colors” like pink/purple on women fly under the radar, so if your gender presentation is female, that might be one way to express yourself. But if you’re in the closet and affirming your sexuality to yourself, what I would think would matter would be art and community. Join some bi groups online anonymously if it’s safe for you to do so. Particularly bi + a shared interest groups. And take in some media that treats bisexuality as “normal” if that’s safe. Here’s a good place to start: https://en.m.wikipedia.org/wiki/Media_portrayals_of_bisexuality

Never forget that you are wonderful and worthy exactly as you are.