Even though Qt doesn't enable fractional scaling on most platforms out of the box, work is being done for it in https://bugreports.qt.io/browse/QTBUG-53022 and users can already override the scaling behaviour with environment variables. We really should make the canvas render properly under fractional DPI scaling.

Qt already uses fractional scaling on KDE Plasma (verified on KDE Neon live environment with appimage), so this is already a real bug on at least one environment.