perfect answer tbh just scrap server logs. sites that offer blogging capabilities as service should do that for their users and provide 'local analytics'. its really trivial to do :/ u get tons of info. if u need more a lot of webservers can also dish out additional logs for you. applications can also be trivially configured to track such things themselves at near 0 cost and effort.

hell, theres ready to use log collectors that will give u even nice dashboarding capabilities if you want to provide more fancy offerings in analytics. if ppl like that so much isnt it an easy sell? non invasive analytics?

(should be noted some platforms do this ofc.. :) )

I was confused by your comment until I realised you meant scrape the server logs, not scrap them