This repo contains a minimal example of how to use your ipad as a remote tablet for linux. There is no need to install anything on the ipad.
For linux the following requirements need to be met.
- rustr
- libgtk-dev
- xdotool
Start the app. Scan the QR code with your ipad. And you're set.
This implementation had a lot of security problems as the data is sent unencrypted and unauthenticated over a local network. If you can't trust your local network don't use it.