Windows 10 (Version 2004, Build 19041.572)

Scaling 100%

"Smooth edges of screen fonts" - enabled

"Turn on ClearType" - disabled

(this corresponds to PixelStructure = 0 in the registry)

Telegram (GDI mode - Freetype looks good)

Picard (started in 2.5.1 - according to the change history they updated to Qt 5.15.1)

OBS Studio

Virtualbox

In the case of Telegram I tried adding

setHintingPreference(QFont::PreferVerticalHinting)

..and that seemed to fix it. Applications shouldn't have to do this though - Qt could detect grayscale antialiasing on Windows and default to the appropriate hinting automatically.