So with FastMail under Australian privacy-bashing laws and now this, what are our options for secure, private e-mail?
Your own self-hosted service on rented server / cloud instance? AFAIU (IANAL!!!) you can refuse to give evidences against yourself in most jurisdictions. I don't thinks that dedicated server provider (like Hetzner) or cloud provider (like Digital Ocean or Vultr) stores traffic logs with enough details to be useful in such case. But payment will be a problem...
One expensive but possible option would be to build a server yourself with sufficient traps to shut off when it's tapered with. Then set it up with full disk encryption and put it in a shared rack.