I feel ya on the PCIe slot. And the on-board NICs are sub-par Realtek garbage, unacceptable both on features and quality. However, you can fit a small SFP+ card inside if you (a) cut out a correctly shaped hole in your case, and (b) turn the fan on at 40% instead of letting it turn off. The card will sit at a small angle but work fine, and with some 3D printing I even got a mounting bracket in to keep it stable. A lower profile connector, like USB 4, might fit outright.

Yeah, I was thinking of running a Occulink connector to the side of the case, the problem is that this would need a riser, and I don't think that occulink - even with a redriver, would do well with two additional physical connectors.

On the 5GB realtek - i think their 5G is far better then their 1g or 2.5g devices where.