After an unsuccessful attempt two active (self-powered) 5m USB to switch 3.0 cables serially, or one of the two active 5m USB with one or two passive 3m USB to combine 3.0 cables 3.0 cables in all possible variants I've been looking for a solution to high probability works.
In the customer recessions, I came across two of the report, the Logitech Webcams behind this 15m USB 2.0 cable can be operated (720p). My findings: The camera is recognized properly, and also runs smoothly at 1080p. (Tested with guvc in Ubuntu Linux)