I have read this existing question: Need default GUI of firefox . It said two things: "Change the proton in about:config" and "uninstall firefox-gnome-theme-maia".
The problem of the first answer is that he never said what value I should use for proton. It showed 3, and I clicked the reset button which changed it to 0, but when I restarted FF, it went back to 3. So the first answer was useless.
The second answer worked, but the problem is that the new tab button is not on the right side of tabs but on the main tool bar next to the “reload” button. How can I change this? I thought that this may be a limitation of Linux, but I can see a Ubuntu screenshot like below, so it should be possible.
