I've got a bunch of Cisco switches with RJ45 connectors for the serial console ports.

Here's the cable they use: https://www.bhphotovideo.com/c/product/1263972-REG/comprehen...

I've got a "Sentry Commander" remote power switch and serial server, with four 6P6C connectors for its serial ports to hook to machines and two 8P8C connectors for its own serial console and modem port. I'm sure it shipped with its own proprietary cables long since lost, but I just use RJ12 cables and those "RJ45"->DE9 modular adapters.