Get the Android SDK with brew cask install android-sdk.
It has a Java 8 dependency and tells you to install it with brew cask install homebrew/cask-versions/adoptopenjdk8.
If you already have another newer version, you must set JAVA_HOME=/Library/Java/JavaVirtualMachines/adoptopenjdk-8.jdk/Contents/Home.
You now have emulator, sdkmanager and avdmanager.
To save yourself the missing file warnings, touch .android/repositories.cfg.
To make a test VM, run sdkmanager "system-images;android-30;google_apis;x86" to get the base image.
You'll have to accept some licenses.