Shell plugins work to ensure that the basic commands Ansible runs are properly formatted to work with the target machine and allow the user to configure certain behaviors related to how Ansible executes tasks.
You can add a custom shell plugin by dropping it into a
shell_plugins directory adjacent to your play, inside a role,
or by putting it in one of the shell plugin directory sources configured in ansible.cfg.
You should not alter which plugin is used unless you have a setup in which the default
is not a POSIX compatible shell or is not available for execution.
In addition to the default configuration settings in Ansible Configuration Settings, you can use the connection variable ansible_shell_type to select the plugin to use. In this case, you will also want to update the ansible_shell_executable to match.
You can further control the settings for each plugin via other configuration options detailed in the plugin themselves (linked below).