Docker (Apple Silicon/M1 Preview) MySQL "no matching manifest for linux/arm64/v8 in the manifest list entries"

Well, technically it will not solve your issue (running MySQL on ARM), but for the time being, you could add platform to your service like:

services:
  db:
    platform: linux/x86_64
    image: mysql:5.7
    ...

Alternatively, consider using MariaDB, which should work as a drop-in replacement like e.g. this:

services:
  db:
    image: mariadb:10.5.8
    ...

Both ways work for me on M1 with the Docker Preview