I forgot to read the second part of your comment so I will make it as a separate comment:

A lot of the “adhd” people I’ve seen online are 200% self diagnosed and use it as a replacement for a personality

Self-diagnosis is the first step to the official diagnosis, stopping at just that is totally not the way to go and I hope that that's not the case for majority of people. Also about the personality thing, when you live your whole life with undiagnosed ADHD and then one day learn about what ADHD does to you you realise that a lot of what you thought is your "personality" is actually ADHD symptoms. So people joking about their personality being ADHD is understandable.

because having adhd is fashionable

Rather than it being fashionable a big part of human population has it and symptoms make it easier to get addicted to social media which makes it seem like there are more ADHD people online than offline. Tbh learning about anything through social media is a bad idea because there's always some kind of bias or misinformation.