Linux puskom-ProLiant-DL385-Gen10 5.4.0-150-generic #167~18.04.1-Ubuntu SMP Wed May 24 00:51:42 UTC 2023 x86_64

/usr/share/themes/Radiance/gtk-3.20/apps/

//usr/share/themes/Radiance/gtk-3.20/apps/libreoffice.css

 .libreoffice-toolbar {
    background-image: none;
    border: none;
    box-shadow: none;
}
.libreoffice-toolbar button:hover {
    background-image: -gtk-gradient (linear, left top, left bottom,
                                     from (shade (@focus_color, 1.5)),
                                     color-stop (0.5, shade (@focus_color, 1.33)),
                                     to (shade (@focus_color, 1.28)));
    border-image-source: url("assets/button-hover.png");
}
.libreoffice-toolbar button:active {
    background-image: -gtk-gradient (linear, left top, left bottom,
                                     from (shade (@selected_bg_color, 1.5)),
                                     color-stop (0.5, shade (@selected_bg_color, 1.33)),
                                     to (shade (@selected_bg_color, 1.28)));
    border-image-source: url("assets/button-active-hover.png");
}