thank you for your answer.
I played around with Settings -> SEO -> Url Management. It does change things, e.g. unchecking "Concatenate Page URLs" results in 4x /uberuns as intended.
My goal of properly replacing the german umlauts "ä, ö & ü" to the corresponding "ae, oe & ue" is wonky at best at the moment, but with a little manual work on the TabUrls table it works fine.