What if a state tries to mandate us as #deltachat app devs/distributors to shut down a chat profile?

Nothing. It can't be done.

We have no list of chat identities, have no handle or data about them, and don't mediate the message transfer.

However, EU #Chatcontrol politicians and Russian authorities would want us to insert backdoors into our FOSS code. But that is nothing than can happen overnight, and we are fine with friendly forks already. Resilient private internet communication ftw :)