user_data cloud-config support and bash support

On various pages and documentation I’ve seen that cloud-init via cloud-config passed in user_data is supported by Ubuntu and CentOS but the docs are all 5 years old or more. For example,

Additionally, the version of cloud-init needed to consume the user-data field is currently only available in Ubuntu 14.04 and CentOS 7

Is there a list anywhere of specific distros that support cloud-init via user_data? And for distros that do not support cloud-config via user_data, will a supplied bash script be run instead if passed? The documentation does not appear to list any limitations:

A string containing ‘user data’ which may be used to configure the Droplet on first boot, often a ‘cloud-config’ file or Bash script. It must be plain text and may not exceed 64 KiB in size.

I’m wondering if I can rely on passing a bash script regardless of what distro I launch.