It is a common scenarion in on prem SharePoint to utilize Information Management Policies at the site collection scope to initiate workflows. Currently there is no way to trigger a workflow from a SharePoint Online retention policy.
Moved from General Flow discussion
We currently use a SharePoint 2010 Workflow to trigger annual review tasks on our policies and processes via Information Policies (for some reason 2013 workflows were never supported). Ideally we could start moving these items to Flow if this function was available.
Was suprised to see how antique the options for Site Content Type workflows are, have not had an opportunity to look at this in a few years but was expecting Microsoft Flow to be a new option for creating workflows to define Content Type retention policies. Seems like the current functionality is just a cut down version of what has been available for the last 12 years - a reduction not an enhancement. Please provide Microsoft Flow workflows for Content Types.