Plausible looks more promising of the two and I will check it out (PostHog could also be, but I didn't really understand the features as it related to a normal WordPress website).
It would be interesting to know how other Plausible users have found their traffic numbers compare vs Google Analytics. Likely that some users would be counted that weren't before, while perhaps bot filtering works differently.
If you are looking to replace Google Analytics with a self-hosted solution (to fully eliminate 3rd parties) you can check out the analytics platform I'm building: https://www.usertrack.net
Could you tell me what was the most important metric missing from userTrack for you? I keep adding new features (eg. just recently added the ability to filter all sessions from a specific user), so knowing which ones are the most common requested is really helpful!
I commented on it because I spotted the Google Ajax calls which sort of lead me to believe that you might have also been using Google for the Geo-Location stuff. When combined with the GA stuff it made me do a 'hang on a minute, something doesn't match up'. Thanks for taking the time to clarify.
That said, we do use the Anonymize IP setting and have all of the demographic / interest settings turned off for Google Analytics.
We basically whittled 3rd party stuff down to GA and a Google font, so while not 100% perfect, I am pretty happy with the strides we have made.