Firefox Client Side Decorations: close, minimize, maximize on the left

userChrome.css

#TabsToolbar {
  direction: rtl;
}

#tabbrowser-tabs {
  direction: ltr;
}

.titlebar-buttonbox {
  display: flex;
}

.titlebar-min {
  order: 2;
}

.titlebar-max {
  order: 1;
}

.titlebar-close {
  order: 3;
  margin-right: 6px !important;
}

The snippet above doesn't seem to work anymore. I use the following in Firefox 72:

/* Turn top bar into flex container, whose contents can be re-ordered */
#TabsToolbar { display: flex !important; }
/* Move x+- to the first position */
.titlebar-buttonbox-container { order: -1; }
/* .toolbar-items contains the tab bar and the other buttons, these should expand to fill the flex container */
.toolbar-items { flex-grow: 1; }
/* Remove spacers, which I don't like the look of */
.titlebar-spacer[type="pre-tabs"], .titlebar-spacer[type="post-tabs"] { display: none; }
/* Re-order the buttons from -+x to x-+ and fix spacing */
.titlebar-buttonbox { display: flex; }
.titlebar-min { order: 2; }
.titlebar-max { order: 3; }
.titlebar-close { order: 1; margin-left: 2px !important; margin-right: 6px !important; }

(Commenting this because this gist is linked from Stack Overflow.)

For Firefox 72 this shouldn't be needed anymore in Linux, where it initially was meant to be used, because Firefox now follows the relative system preference and moves the three buttons to the left if needed.