If you're particularly security-conscious or just want a cool DIY project to make use of that old monitor, how about turning it into a privacy screen?

Sidecar in macOS turns your iPad into a second display, but it's limited to certain Macs and iPads. Thankfully, a few third-party apps can help if you have an older Apple device or Windows PC.

The second screen is a slimmer version of the first case, with a different board that has an onboard audio channel.