Barrier

Ubuntu 20.04
sudo apt install barrier

Setup
Install Barrier in all the machines! When done, open it, choose your language and then select either Server or Client.

Server
Select “Server” on the machine that connected with the mouse and keyboard. And all others set to “Client”.

On the server computer, click on “Configure Server…” button.

n the screen configuration page, you have to drag and drop small “computer” icon into the grid to add clients.

The center one is the server screen. Drag & drop ‘computer’ icon to create client screens. Double-click to rename client screen name (check in client machines, usually computer name). Move client screens around the server (left, right, top, bottom).

In the case (as picture shows), when I move the mouse cursor to the left screen edge in server, the mouse & keyboard will take control of “fedora” machine. In “fedora”, move to the right screen edge will go back to server machine.

As well, move the cursor to the right edge in server will go to “Desktop-PC”.

In the “Hotkeys” tab, you can configure keyboard shortcut to switch screens.

First click ‘New’ and create a shortcut key. Second highlight the key you created. Click ‘New’ in right to specify an action to perform.

And you can get optional settings in the ‘Advanced server settings’ page.

Client
It’s easy to configure the clients since it supports ‘auto config’. Just click start, it will automatically connect to the server if available, and prompt you to trust the fingerprint if SSL enabled.

By disabling ‘Auto config’, you can type server IP manually. And a dialog will pop-up indicates you connected successfully.

For connecting issues, check the log from menu. As well, you can change the listening port, toggle SSL via settings menu.