I found out that being able to let go of things relieves a lot of load over one's proverbial and literal shoulders.
https://hluk.github.io/CopyQ/
Either way, I think it is better to not copy passwords to the clipboard or the selection, but store and transfer them via password-manager/browser/etc APIs.
https://codesearch.debian.net/search?q=x-kde-passwordManager...
Wish it was a protocol-level setting, though, instead of something KDE specific and honored at the application level.
I found out that being able to let go of things relieves a lot of load over one's proverbial and literal shoulders.