I moved over to Proton from Google because I liked the idea of having an alias for each service.
You can pay less than $1/month for domain (i.e. on Porkbun or Cloudflare) and have unlimited email forwarding for services. Just set up catch all and forward that to your Proton/Gmail. And your own domain might be useful for you in future.
They mean the iPhone’s MAC address, right?