Voultar has claimed that the mod sold by console5 is stolen from his design, so I would think it would work the same, though the mods I see on their respective sites look rather different on their face, with Voultar selling two separate mods for SNES and N64 while console5 sells a combined SNES/N64 mod. As far as the components and functionality, I’m pretty clueless. It looks like sync on the console5 mod is straight off the SNES optionally attenuated through a resistor, I suppose to adjust it for 75 Ohm termination instead of TTL level sync? While Voultar’s description says his mod automatically adjusts for 75 Ohm or TTL based on the cable you use, which sounds like some black magic to me.
Maybe that black magic is what makes it work with your cable. The obvious question with the console5 mod would be whether you’ve set the TTL jumper to be compatible with your cable. But how do you even know with some random cheap cable where it’s getting sync and (if getting it from CSYNC) whether it expects TTL or not? If the cable syncs on luma or composite, then the CSYNC signal would be irrelevant.
Do you know where your DHCP server is? What are you plugging your Debian server’s network cable into? I understand that networking apparently worked while you were installing Debian, and it’s unclear why that would have changed, but if I were in your position the first things I would suspect would be something with the DHCP server itself (like it stopped running or ran out of addresses), or a lack of connectivity between the Debian server and the DHCP server.
In other words, I’d start troubleshooting with your network, but it’s hard to suggest specifics because we don’t know anything about your network. One simple thing to try might be to restart your router. For most home networks, that’s where the DHCP server will be, and it should start up on boot.