How to use your iPad as a second monitor on any computer

Two monitors are better than one, and with macOS Catalina, you can turn your iPad into a second display with just a few clicks thanks to a feature known as Sidecar. But Sidecar is limited to certain Macs and iPads, which is a bummer if you have an older device (or a Windows PC). Thankfully, a few third-party apps can help fill...