In KF5 5.81, autoAccept was introduced on the SearchField, which spams the accepted signal as fast as the user types by default. This causes bugs/lag/breaking in applications that expect the text field with preset defaults to work like a text field.
For such applications, you can set autoAccept to false, no?
Answering my own question: yes you can.
This was mostly reported as a “you broke existing applications” rather than “this behaviour on its own is bad” but it’s obsolete now since KF6 and all.