I've been using serial-to-Ethernet device services for connecting embedded devices and "retro" computers to modern networks and PCs. They're much more expensive

I've been using serial-to-Ethernet device services for connecting embedded devices and "retro" computers to modern networks and PCs. They're much more expensive than USB-to-serial cables, but much more flexible (since they're independent IP-based devices). The particular one I like, from Lantronix (https://www.lantronix.com/products/xdirect/ https://www.lantronix.com/products/xdirect/) supports power-over-Ethernet and has a really nice feature-set.