If I'm not wrong you can configure KeepassXC to only store credentials in the clipboard for a selected timespan (like 5, 10 or 30sec). You can also eliminate it entirely IIRC by using the autotype feature when entering credentials.
Autotype do not suffer this problem and is generally considered safer. Some password managers have an even safer "mixed" mode where part of the password is in the clipboard and another part is auto-typed, meaning you have to monitor both the keyboard and the clipboard to grab the password
(I'd prefer the clear/overwrite myself.)
Another option would be specific IPC such that clipped content is available to one and only one other application or process. There was a recent HN submission on the Unix password manager utility "pass", including the ability to supply passwords to a command via shell expansion rather than as a command-line parameter. The former doesn't reveal the password in either process listings or shell history, the latter does.
That's a relatively primitive option, a more robust standard might also be provided.