I "only" have Hybrid7 from Init7 - so I don't know if this also applies to Fiber7. However, it is the case that for Hybrid7 it is not sufficient as the only device. It still needs an optical-to-copper signal converter and also PPPoE must be used in the DreamStation when configuring the WAN connection (DHCP is not supported by Init7 for Hybrid7). The problem is, Init7 requires a special VLAN ID, which unfortunately cannot be configured via the DreamStation's setup wizard. I had to connect the DS to another router to get through the initial setup wizard. I was then able to set the VLAN ID in the system settings and connect the DS directly to the internet again (i.e. without an intermediate router).
The manufacturer Unifi probably didn't think this through or simply implemented the software badly.
The best thing to do is to briefly check with Init7 whether the setup via DHCP works with Fiber7. If not, and you also have to do PPPoE, then you need a second router temporarily for the initial setup in order to be able to set up the device at all.