SelfHosted analytics
As usual I start with Awesome-Selfhosted. This created a short list of 3 solutions:


On the Ghost Forums there was a Idea to integrate analytics, the same 3 solutions were also mentioned there.
Matomo has a lot of features that I do not need. Plausible has a Community Edition that can be SelfHosted, but the compose file looks complicated.
So I decided to start with Umami. I used their compose file as an example. What I did not consider is that postgres needs a bit more resources than expected. So when I added the 2 services to the same VPS as where Ghost is hosted, the VPS had a load of 50. So I quickly stopped these docker containers.
Luckily I had already setup Pangolin last weekend so I can publish applications that are running on more powerfull hardware at home. Once this was running, login with the default credentials (admin/umami), change the password and add the domain. Then include the tracking javascript in the Ghost headers and tracking is now working:

PS: I have planned to move to a more powerfull VPS soon so I can host Umami on the same VPS as Ghost.