this is all true, but i'd like to add: if you're considering getting an official test and not just taking an internet one....please consider the cost-benefit analysis seriously. (this goes for all neurodivergences tbh--reminder that "neurodivergence" is not a synonym for "developmental disability" let alone "audhd"--but since those were brought up here and they're really representative of the extremes i'll focus on those)
ADHD tests are generally safe and worth it. ADHD diagnosis doesn't generally impact immigration applications, organ transplants, etc. You are unlikely to experience medical abuse due to an ADHD diagnosis. You are very likely to be offered stimulants, which are usually considered extremely helpful but are gatekept behind a diagnosis, making the diagnosis actively useful-- but, as an adult, you're extremely unlikely to be forced or coerced into taking them if you don't want them or find the side effects to be too much for you.
Autism diagnosis is not like this. while it's much less likely to be a problem if you're low-support enough that you are able to choose to get a diagnosis or not in the first place based, an autism diagnosis has major downsides and significantly more limited upsides. depending on the exact countries involved, it can restrict immigration options if you're unable to prove low healthcare costs or make immigrating more difficult even if you are. you may be deprioritized for organ donation. you're likely to face increased medical gatekeeping and medical abuse rates in general; if you're transgender, there's been a major international push for the past decade or so targeted at gatekeeping transition more strongly for autistic people (explicitly including autistic people with lower support needs). on the flip side, there is no medication or therapy that i'm aware of that is both particularly useful for autistic people and gatekept with diagnosis. in most of the US, the only therapy covered by insurance for autism is ABA, which is considered by many autistic self-advocates to be abusive; more commonly among late-diagnosed, low support needs, "level 1" autistic people, you will just be recommended regular talk therapy, ideally with someone who has experience with autistic clients; this does not require an autism diagnosis. there are no medications specifically aimed at treating or curing autism, and if you present as "level 1"/"high functioning", it's unlikely that you will be prescribed medications like antipsychotics for controlling symptoms. (though, like.....let's just say i have my own opinions on the use of risperidone for behavioral control. it's certainly not an unalloyed positive. and if you are prescribed medication for your autism, you are in a position where it's relatively likely that you will be forced or coerced into taking it if you do not want it.) most likely, the process of seeking an autism diagnosis is the experience of paying potentially thousands of dollars for a reward of...being discriminated against.
this is not to say there are no concrete benefits to an autism diagnosis. if you need accommodations, disability benefits, or autism-specific resources in your community, and cannot get them without an autism diagnosis: please don't let me stop you! but if you are just looking for validation and self-acceptance as a "quirky" adult.... seriously consider sticking with independent research and self- or peer-diagnosis before getting officially diagnosed with autism.
most neurodivergences are somewhere between autism and ADHD in terms of how useful vs costly they are to get diagnosed as an adult. a dyslexia diagnosis can be helpful if you need accommodations in your workplace, and an adult dyslexia diagnosis is relatively unlikely to result in serious discrimination or abuse, but depending on your job it also may not come up much or you may be able to get accommodations without official paperwork, there aren't (AFAIK) specific treatments that are gatekept by professionals, and the monetary cost of evaluation can get expensive. a diagnosis of bipolar can open you to discrimination in immigration, medicine, etc., but it also opens up treatment options that would not otherwise be available, and the initial evaluation is generally less expensive than for learning or developmental disorders. consider what you need, what costs are small vs large for you and which would be likely to come up, and whether diagnosis is right for your specific situation. and while i can't stop anyone from getting diagnosed purely for validation or self-understanding--these are genuinely valuable things!--i have to also strongly recommend considering what the material effects of testing and diagnosis will be on your life, both positive and negative.