SUMMARY
The plasma disk and devices applet does not seem to follow the BinaryUnitDialect config option. Normally it is just a matter of replacing some function with some higher-level ones.

STEPS TO REPRODUCE
1. Set BinaryUnitDialect=2 in [Locale] section of $KDEHOME/.config/kdeglobals (setting to metric/SI instead of IEC)
2. Look at applet with some storage devices plugged in
3. Look for size info underneath device name

OBSERVED RESULT
GiB is used instead of GB (the latter would be correct given the described settings in $KDEHOME/.config/kdeglobals)

EXPECTED RESULT
Metric formatting is used

SOFTWARE/OS VERSIONS
KDE Plasma Version: 5.24.6
KDE Frameworks Version: 5.96.0
Qt Version: 5.15.5

ADDITIONAL INFORMATION
The BinaryUnitDialect config option is described in Bug 57240. This option is for now still without a GUI, but Bug 364321 makes it clear this is about to change. So apps like the plasma disk and devices applet should be made ready to follow BinaryUnitDialect.

It may be that there are other plasma components that need the same fix applied.