Does anybody know what influences the font size of Firefox UI elements on Debian/Gnome? I have layout.css.devPixelsPerPx set to 1.5 and I wonder whether the new Firefox 115 I have is now applying the setting to its UI, too. Assuming that both web pages and UI are now controlled by the same setting (which I can't change because I want to read the web pages), I guess I need some CSS help for userChrome.css so that I can set the font-size for just the UI. This seems to fix the problem (the font-size: 10pt part, specifically):

@-moz-document url(chrome://browser/content/browser.xul),
               url(chrome://browser/content/browser.xhtml) {
    * { font-size: 10pt }

    /*** Tighten up drop-down/context/popup menu spacing (8 Sep 2021) ***/

    menupopup:not(.in-menulist) > menuitem, 
    menupopup:not(.in-menulist) > menu {
      padding-block: 4px !important; /* reduce to 3px, 2px, 1px or 0px as needed */ 
      min-height: unset !important; /* v92.0 - for padding below 4px */
    }
    :root {
      --arrowpanel-menuitem-padding: 4px 8px !important;
    }
}

#Firefox