Dennis I have been successfully using Plausible Analytics. It's not free however, but there's a free trial. You get 10k page views for $6 per month, which let's me easily monitor several small websites.
I especially like it because it's very lighweight and privacy friendly. The integration in Automad is done in an instant for you only need to add a single line of script code (copied from the Plausible's administrative interface) into Automad's 'Default Template Settings' as additional markup to the Item's Header.