EDIT: Fixed the dropdown by nuking line 15, still trying to solve the selection highlighting turning green again

My userChrome:

menupopup:not(.in-menulist) > menuitem, 
menupopup:not(.in-menulist) > menu {
  padding-block: 0px !important; /* reduce to 3px, 2px, 1px or 0px as needed */ 
  min-height: unset !important; /* v92.0 - for padding below 4px */
}
:root {
  --arrowpanel-menuitem-padding: 0px 0px !important;
}

/* Make urlbar appear more compact */
#urlbar[breakout]{
  margin-inline-start: 0px !important;
  width: 100% !important;
  left: 0 !important;
  top: calc((var(--urlbar-toolbar-height) - var(--urlbar-height)) / 2) !important;
}
#urlbar[breakout]:not([open]){ bottom: calc((var(--urlbar-toolbar-height) - var(--urlbar-height)) / 2) !important; }
.urlbarView{ margin-inline: 0 !important; width: auto !important; }
.urlbarView-row{ padding: 0 2px !important; }
.urlbarView-row-inner{ padding-inline-start: 4px !important; }
#urlbar-background{ animation: none !important; }
#urlbar-input-container{ padding: 1px !important; height: 100% !important; }
#identity-icon{ margin-block: var(--urlbar-icon-padding) }
.urlbarView > .search-one-offs:not([hidden]){ padding-block: 0px !important; }


#nav-bar:-moz-lwtheme #urlbar ::-moz-selection,
#nav-bar:not(:-moz-lwtheme) #urlbar ::-moz-selection {
        background-color: #3040cf !important; /*it's green again; want to fix this too*/
    color: white !important;
}

/* Set blank page background-color */
/* Uses color from theme_colors if available */

#tabbrowser-tabpanels{
  background-color: var(--uc-light-bkgnd-color,rgb(0,0,0)) !important;
}
  • @MrOtherGuyEnglish
    2•21 hours ago

    The non-standard :-moz-lwtheme is now considered invalid syntax, so using that invalidates the whole ruleset it’s used in. Featurewise the equivalent would be to check for existense of lwtheme attribute on root element. But the way you have written your rules the you have never even needed :-moz-lwtheme selector to begin with since you are applying the same rules when that matches and doesn’t match. So you can just write this to get your desired selection color in urlbar:

    #urlbar ::-moz-selection{
  background-color: #3040cf !important; /*it's green again; want to fix this too*/
  color: white !important;
}