This is less about the Clipboard manager though, and more about the system’s own clipboard functionality itself:
hiding or disabling the Clipboard manager does nothing about disabling common keyboard shortcuts (CTRL+X/CTRL+C/CTRL+V) or common context menu options (Cut/Copy/Paste).
At least under Wayland (and possibly Xwayland), it would seemingly be possible to globally disable all clipboard functionality across all selections (PRIMARY, SECONDARY, CLIPBOARD).
I certainly agree that it would be a useful feature to have for certain usecases, I discussed this a few days ago here: