[KevinH]

I just pushed that change to master along with this earlier snippet from Sigil's main.cpp as well:

#if !defined(Q_OS_WIN32) && !defined(Q_OS_MAC)
    // Unset platform theme plugins/styles environment variables immediately
    // when forcing Sigil's own darkmode palette on Linux
    if (!force_sigil_darkmode_palette.isEmpty() ||
        !force_pageedit_darkmode_palette.isEmpty()) {
        QStringList env_vars = {"QT_QPA_PLATFORMTHEME", "QT_STYLE_OVERRIDE"};
        foreach(QString v, env_vars) {
            bool irrel = qunsetenv(v.toUtf8().constData());
        Q_UNUSED(irrel);
        }
    }
#endif

That appears to work on my Manjaro box under Qt6 and Qt5 with FORCE_PAGEEDIT_DARKMODE_PALETTE=1 set.

Hope that is okay.