Need recommendations from UK MG authors on neurodivergence and choice of words

I’m working on a middle grade epic fantasy novella with a young protagonist who is neurodivergent. I had a UK beta-reader who raised a concern on using the word “dumb” in this type of story as it has some baggage there. I used it some times to either have characters or the character himself to criticize some of his action as not the wisest, but not in the context of his condition. Note that the character’s condition doesn’t affect his cognitive abilities.

e.g. (paraphrased)

“I shouldn’t have betrayed him. That was dumb of me.” (POV = lead)

“I’m not as smart as Johnny but even a blind squirrel can that see this is a dumb deal.”(Context = different character criticizing and another. Both are not neurodivergent, but Johnny is)

The beta reader acknowledges that the usage doesn’t have the same connotation in the US, but that I would like to get opinions/recommendations from UK authors as the last thing I would like to do is alienate part of the audience I would like to reach with a positive and uplifting message.

Carlos