The Cheap, Cross-Platform Option : Splashtop Wired XDisplay | Life Hacker

The Cheap, Cross-Platform Option :

Splashtop Wired XDisplay

If your Mac or iPad isn't supported by Sidecar—or you're a Windows and Android user—Splashtop Wired XDisplay is a third-party app that can turn your tablet into a second monitor. It only works when connected over USB, and isn't the smoothest option I've used, but it'll do the job adequately for not a lot of money.

Splashtop Wired XDisplay has two components: a desktop agent that runs in the background on your PC or Mac, and an iPad app or Android app that runs on your tablet. (The iPad app appears to be completely free, while the Android app is $7—though there's a free trial version that works for 10 minutes at a time.)

After installing both the desktop and tablet apps, ensure the desktop app is running on your computer, connect your tablet to your computer with a USB cable, then launch the XDisplay app on your tablet. It will establish a connection to your computer, and a blank desktop will appear on your tablet. You rearrange your monitors from your computer's Display settings, drag windows to your tablet, and otherwise use it as a second monitor for a productivity boost.

I recommend having a stand to keep it propped up—something like this works great if you're using your tablet with a laptop, while a more adjustable stand like this is ideal for desktop usage.

Splashtop Wired XDisplay works decently well, at least in my experience using an iPad and a Windows PC. There is some noticeable latency, and I did have some trouble with it getting stuck in Mirrored Mode on one of my computers, but for the price of free, it's worth a shot.