[KevinH]

The issue with stylesheet may be caused by Sigil/src/Misc/SigilDarkStyle.cpp which does the following:

void SigilDarkStyle::polish(QApplication *app) {
    if (!app) return;

    // loadstylesheet
    QFile qfDarkstyle(QStringLiteral(":/dark/win-dark-style.qss"));
    if (qfDarkstyle.open(QIODevice::ReadOnly | QIODevice::Text)) {
        // set stylesheet
        QString qsStylesheet = QString::fromLatin1(qfDarkstyle.readAll());
        app->setStyleSheet(qsStylesheet);
        qfDarkstyle.close();
    }
}

Everywhere else we effectively do:

app.setStyleSheet(app.styleSheet().append(NEW_STYL E_INFO))

which prevent overwriting of any earlier stylesheet info at the application level.

We should probably change that to be safe to prevent overwrites of stylesheet contents.