[This](https://fosstodon.org/@linmob/109047389151432165) mastodon conversation mentions that QT/QML apps can turn all black, especially while scrolling, and this workaround of QT_ENABLE_GLYPH_CACHE_WORKAROUND=1 can fix it on the PP. This one is a PP-specific workaround, I am not sure if it is a problem on the PPP too. While we are at QT environment variables, we probably also want to set: QT_QUICK_CONTROLS_MOBILE=1 at the same time. Apparently pmOS also set one or the other variable already.