Hi, folks.

Find a solution, pretty plain and dumb, still worked for me (Kubuntu 20.10):

1. set 'Clipboard history size' in the General Settings tab to '1'.
2. ok, clipboard now always keep the last value.
3. bound a small script (random string -> copy to buffer ) to a hotkey and don't forget to press 'Eat it Clippie', every time, after copy-pasting essential data.

Yes, this is ridiculous, still works)