They wont diagnose in the UK without symptoms shown in childhood but it is self reported / reported by parents / shown in school reports.
Also from personal experience being diagnosed as dyslexic at 9 made my school think all my problems were dyslexia related and nothing else. Only diagnosed ADHD at 30.
If your in the UK (not Scotland because it doesn’t apply) search “the right to chose ADHD law” you can skip the UK waiting list and be assessed with in weeks/months with private healthcare providers which is paid for by the NHS.
There is one psychiatrist firm that supply you with the paperwork you need to take to the GP for free to get referred.