Thanks very much for pointing me in the right direction.
I managed to build the drivers using the famous instructions from linuxtv.org as well as the very important hints from @mometto in another thread. Specifically, I had to create a symlink for the headers and download the complete kernel source and copy a mach directory as described by @mometto.
I see block artifacts every couple of seconds, so I’ll try to use a better coax cable (inspired by this post).
BTW, it took ~45 minutes to compile the V4L drivers on the Raspberry Pi 3 with a class-10 microSD card.