None of the keyboard shortcuts for changing layer blending modes as outlined in https://docs.krita.org/Blending_Modes#Hotkeys_associated_with_Blending_modes and listed in Settings->Configure Krita->Keyboard Shortcuts->Blending Modes work by default. This forces use of GUI to change blending modes.
Yes, I can confirm this, despite them being set.
The shortcuts are not for changing the layer blending mode, but for changing the painting blending mode, and for that, they do work.