Ah, don't have a modem in front of it, but its built in. Sorry on that one, my bad. I guess that's what explains the reason I get the line to come online when plugged into the DSL port. Moving from that, my only issue then is how to configure that DSL port to use DHCP with VLAN ID 7 since I can't see it in "Network -> Switch". Or is it simply not possible and I NEED a separate modem?
I'm using a FritzBox 7530 with a build from here (github source) because the modem inside it is still not supported in the official repo, but the PR is already on the official repo with people showing that its working in the forum thread. I guess I can also confirm this since I get the DSL Line to come online under DSL in Status.