This guide will let you know how you can invite your friends in Escapists 2 game.
You have to click on the PLAY GAME first, then select any prison that you want to.
After that, tap on a NEW GAME, and click on the empty slot. Select the PLAY MODE as private and then start the game.
Select your character to start the game and then press the Esc key on your keyboard. You will find a friends list on the right side of your screen, click on any friend and invite him into the game.
Your friend will get a steam message, he will need to press shift and tab to open it up and then join the game.