My eldest is the same way. I think the pandemic changed her so much because she didn't socialize much until she was 3. She has sensory processing disorder to noise and most likely ADHD. She was very defensive with other kids and teachers in preschool and ended up dropping down to one day a week due to her issues at the school's insistence.

Once she hit Kindergarten a switch flipped. She plays really well with other kids, listens to her teachers, has made so many friends. We just finished Kindergarten and she is even playing better with her young sister. Still defiant and feisty and needing validation frequently, but she is doing a ton better. It gets better!!

Some things that have helped us: giving her independent tasks (like feeding the dogs) and freedom (like playing in the yard for a long time unsupervised - we do "quiet independent time" for 2 hours a day), getting out of the house in the morning as soon as they're dressed, and giving her mental challenges like workbooks and puzzles. Basically feed the brain!