The new 'Only show games available on this platform' checkbox in the
plugin settings drops games whose platforms don't include the OS
OpenGamepadUI is running on (e.g. Windows-only games on Linux). Games
with no platform info at all (HTML5) are kept since there's nothing to
filter on. The setting is read on every library load, so toggling it
reloads the itch.io library without a restart.
OGPU wipes user://plugins/<id>/ (and everything inside it) whenever a
plugin is updated or re-extracted, so storing butler and butler.db under
user://plugins/itch/assets meant every version bump deleted the binary
and its login session. Store them in persistent user://butler instead,
and migrate any leftover install from the old location.
