The Centro Grande can do "IP passthrough". It is then possible to operate the Swissom TV box on the Swisscom router and the router itself also receives the public IP address. This has worked problem-free for us for about 7 years.

Swisscom is satisfied because they don't have to deal with any special configuration and I am satisfied because I can do any configuration on my router (VPN/NAT or whatever).

As far as I know, you need a modem in between.
I had the same router when I was still a subscriber to gga-maur (fibre optics).
Since I've been with Swisscom (DSL), I've been using the Swisscom router with integrated modem/WLAN. I have sold the RT-AC68U.

So I have this router with a Wingo fibre connection. Without Wingo modem. Works perfectly.