Desktop app with server and package installer NO AGENCIES

I need a programmer to develop a cross-platform Windows/Linux/Apple desktop application that mimics one of our website's functionality when offline, but synchronises with it when online.

In essence the project consists of a simple outliner as displayed in the attached image, a small local secure Linux server, and a network connection to our cloud database. The server must be set up for PHP with Laravel framework. The finished development must be scripted into a package installer and the client machine server started after installation and on product start-up.

Developers must speak clear English language plainly understandable to the British ear and a good Internet connection for development meetings by Zoom. After success and testing there may be another project to do the same for mobile devices.

This is not a difficult project but must be secure. To apply, let us know your approach, language, package installer, what the user will see during the installation process, and price.