The comments that the 6690 Fritzbox cannot be set up as a modem + router like the 6660 put me off buying it in the first place. The technician (GIB Solution) told me that they can send me a "cable only" modem in exchange and then I can connect any wifi router.

In my case, the cable provider (Sasag Kabelkommunikation AG in Schaffhausen) did not authorise the modem. Due to the 10% return fee charged by Digitec, an exchange is hardly worthwhile. I therefore use the Fritz!Box as a WLAN router and recommend the Fritz!Box 4060 to everyone, which is cheaper and can be used as a WLAN router with all Fritz functions.

I would be interested in that too, because I don't know of any.

I wonder about that too, is there a free choice of router like in Germany too ?