TL;DR: caprover does NOT run on Strato Linux VServer (e.g. Linux V10). Think about nginx reverse-proxy, certbot and docker-compose instead.
The whole idea of running my own server was to install caprover and then be able to easliy create and push web applications. However, it did not work as intended…
This is a note to everybody that tries to install caprover, a self hosted PaaS (something like heroku) on a Linux VPS hosted on strato: It does not work.
The Strato VPS Linux servers, e.g. Linux V10, seem to be docker containers themselves (This might be the reason, why one can rent such a server at the low prize of 5 EUR/month). Caprover however would need to be installed on a non-dockerized host machine. Inside a docker container, the swarm and networking capabilities seem to be restricted.