[simonhorlick]

You need to ask him what accommodations he needs in order to be effective. Only he can really answer this question.

It could be small things like clearly indicating your intent - avoid sarcasm, figurative language and idioms. In a group chat this could mean adding "/joke" to messages. Autistic people generally like structure. Ensure your task tracker is clean and to-the-point. The benefit of this is it also help non-autistic colleagues.