By default, the ansible-doc command will use module as the type, thus the -t or --type option followed by strategy must be used to display documentation on strategy.

The -l or --list option can be used to list the strategy documentation.

ansible-doc --type strategy --list

debug       Executes tasks in interactive debug session
free        Executes tasks without waiting for all hosts
host_pinned Executes tasks on each host without interruption
linear      Executes tasks in a linear fashion

Let's say you want to learn about "linear". The -s or --snippet option can be used.

ansible-doc --type strategy --snippet linear

• Refer to Ansible - Free Strategy for more information on the free strategy.
• Refer to Ansible - Linear Strategy for more information on the linear strategy.