Hardware

Per the video though, the problem clearly is Windows' ability to enumerate the serial devices and assign COM* port numbers to them. Linux might do a bit better there, although looking at my Ubuntu systems the hard-coded maximum serial port count is 64 (adjustable by recompiling the kernel, at least).

In any case, that is only an attempt (as they say themselves) to maintain period accuracy. If you ignore that, you'd probably have a much easier time with USB modems connected to either a bunch of hubs, or a handful of multi-port PCI(e) USB cards.

Also - and we are getting extremely off-topic here - individual Epyc CPUs allow 128 PCIe lanes, but 48 or 64 are used for the inter-socket link in a 2S system, leaving a maximum 128 or 160 available as external connectivity. A moot point anyway as PCIe switches exist, and can be found in all manner of hilarious expansion chassis that could allow hundreds of PCIe cards even on a desktop system: https://shop.bressner.de/en/products/hpc-solutions/gpu-computers/gpu-expansions/gen5-4u-pro-16-slot/