Hey @pjrobertson,
the input on top of the page list (top left in the Collectives app) is merely for filtering the page list by page titles.
Searching for collectives, page titles or page content works via the unified Nextcloud search (top right corner). If searching for page content doesn’t work, make sure you have the ext-pdo and ext-pdo_sqlite PHP extensions installed and the Nextcloud cronjob is running. The index of collectives page contents should update with every cronjob run.