I do use KDEConnect.

I didn’t consider that. It may be syncing my clipboard to my phone and back.

Is there an option to send the clipboard contents without permanently sharing the clipboard?

This doesn’t help me. It’s specific to keepass and is user error in using the clipboard to copy instead of keepass’s copy feature.

My case may very well be user error, but I can’t find a solution for it. It seems to keep a history of the last thing copied regardless of what I choose.