Based on our record, Air Display seems to be more popular. It has been mentiond 3 times since March 2021. We are tracking product recommendations and mentions on various public social media platforms and blogs. They can help you identify which product is more popular and what people think of it.
Https://avatron.com/applications/air-display/ Not sure, if it does screen mirroring. Source: almost 3 years ago
If you're talking about Target Display Mode, I'm afraid your iMac does not support it. You can still use something like Air Display, although I'm not sure if it will help you achieve what you want. Source: over 3 years ago
The other option is via software like AirDisplay, but that does cost money as well! Source: about 4 years ago
Duet Display - With Duet Display, you can transform your iPhone or iPad into a second display to expand the screen space of your PC or Mac system.
spacedesk - spacedesk expands the Windows desktop computer screen to other computers over the local area...
iDisplay - iDisplay is an app that turns a mobile device into a secondary desktop monitor. The app currently supports iOS, Android, Windows and MacOS, and it lets users connect a desktop computer to a mobile device over WiFi. Read more about iDisplay.
Splashtop Wired XDisplay - Use Splashtop Wired XDisplay to turn your iPad, Android tablet, Kindle or smartphone into a high-performance extra monitor for your computer.
Luna Display - Hardware that turns the iPad into a wireless second display
TwomonUSB - You can create dual monitors quickly and easily using a USB.