There is no module in Ansible called linear, only the strategy plugins
has that name.
All modules in Ansible is listed here
https://docs.ansible.com/ansible/latest/modules/list_of_all_modules.html
A search in the source code
$ find git/ansible/ -iname '*linear*'
git/ansible/test/units/plugins/strategy/test_strategy_linear.py
git/ansible/test/integration/targets/strategy_linear
git/ansible/lib/ansible/plugins/strategy/linear.py
Just the linear strategy
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Kai Stian Olstad