When it comes to networking and plugin modules, there’s a popular standard: SFP transceivers.
See: wikipedia
Will SFP modules be supported? There are optic fibre modules, and I can’t think of ANY other laptop that even comes close to offering optic fibre network support.
Might be able to, expensive. StarTech USB C to Fiber Optic Converter for Laptops - Open SFP | US1GC30SFP | JW Computers Would have to crack one open and look at the internals to figure it out.
The SFP cage height is a bit too tall and long to realistically fit in this laptop, and I have not experienced a lot of SM fibers, and the associated LC connectors, that are designed for a high number of plug/unplug cycles. So I would recommend going with a usb 3 or 4 expansion card/dongle that has a SFP cage. 10gbit fiber/gbe networking is awesome 
I love it.