I mean, ADHD is very commonly a co-morbid condition with other neurological conditions. It's more uncommon to NOT also have ADHD when you have another.
Executive functioning problems happen in both autism and ADHD, so it could be autism related or ADHD related.
At one point I asked my therapist, how can you tell if something is related to ADHD or autism if you're diagnosed with both or suspect both? And she was basically like 'there's not really a way to tell and it comes down to subjective judgements.'
🤷♂️ I'm more of a practical person. If ADHD coping techniques or medication help you, does it matter which it technically is?
I got diagnosed with both around the same time. It's not impossible to have both, so I'd look at some qualified doctors on YouTube and see if what they describe as ADHD is how you feel.