And that said, if you want to make something looking vintage with new stuff, you could (as some have done) just use a RPi, a mechanical keyboard, a USB-RS232 adapter, and whatever monitor looks vintage to you (if that matters.) Of course you may need some HDMI-to-whatever interface this old monitor has. You could even mount the RPi and additional adapters inside of the monitor case, and just add a plug for the keyboard, to make that look definitely like a vintage terminal. Software-wise, you'll just need a terminal emulator - I think there are tens or hundreds of them on Linux.
Actually, if the monitor's resolution is modest (as was usually the case in those vintage terminals) and monochrome only, you could even use a microcontroller instead of a RPi, and have it generate the video signal.