How do I grep the CiviCRM universe?
You can use build kit to generate a repo including the civi "universe"  https://docs.civicrm.org/dev/en/latest/tools/universe/

civibuild create universe


or

mkdir ~/src/universe
fetch-universe ~/src/universe


could be worth checking extension usage to see if there are any widely used ones that don't make the cut to get included.

Happy grepping!