The best alternatives to Shiftscreen are Astropad, iDisplay, and Lunar. If these 3 options don't work for you, we've listed a few more alternatives below.
Astropad will be your graphic design tablet for your Mac! Draw directly, with no compression, in Photoshop from your iPad. This tool allows you to connect your Mac and your iPad together to create the perfect working space! No lagging, only high-quality clear images!
The built-in display brightness of your Macbook or iMac is synchronized to the external monitor.
Custom brightness and contrast values are computed for each external monitor by passing the built-in brightness through a curve algorithm that is completely configurable by the user.
World’s thinnest and most portable touchscreen displays. It turns your laptop into a portable workstation! Its premium grade aluminum design is lightweight, so you can take it with you just about anywhere; your next flight, a coffee shop or even right at home.
Get an extra screen using your iPad. Yam Display turns your iPad or iPhone into an external display for your Mac via USB. Yam Pad turns your iPad into a Drawing Tablet for Mac with Apple Pencil. Yam Air enables wirelessly.