I also have this problem where I can't maximize for whatever reason. I can minimize and maximize briefly while it's loading up and displaying the Godot logo. But afterwards the maximize button vanishes for me. I would assume you have resizeable checked in the project settings since it works on Windows.
I am not able to replicate this issue with Godot 3.3.2 under Linux. Have to check the github and see if anyone else is.
One option I could recommend as a temp fix. Is you could allow us to go into Fullscreen. While not really ideal but be an okay option for people who want to be able to see the bottom bar.