TikTok does have a ton of misinformation, projections of learned helplessness, and recommendations of pseudoscience/under-studied treatments; but if you are a TikToker and really want to get ADHD tips there, here are a few users I've found that actually seem to know what they're talking about:

HowToADHD (Jessica McCabe)
The_ADHD_Nutritionist (Marley Alex)
ADHDVision
ADHD_Coach_Ryan (ADHD Coach Ryan Mayer)

Though even with them, take what they say with a grain of salt, do your homework, and talk to your doctor/therapist/executive function coach before implementing stuff that may impact your wellbeing. Also, be mindful of recommendations that are also paid sponsorships.

I follow a couple more, personally, but I don't feel comfortable recommending them because their suggestions and the information they provide can be a bit dubious at times.