Comment by mircerlancerous

Neat project, regardless of some of the opinions of practicality.

What you want to do is make sure your client device is an HID device, so that it's recognized as a keyboard. I think something like this will do: https://makerspot.com/cp2110-usb-hid-to-uart-serial-adapter/

For the server side, you'll either want a USB to serial adapter with a microcontroller in between, or one of the RP2040 Raspberry pis as it can be both those at once. https://www.waveshare.com/rp2040-zero.htm

Actually you can probably do it with two RP2040s (or maybe just one) as their USB ports I believe can be configured for different roles.

Good luck, and share your results!