Comment 3 for bug 1963868

For me, the search bar doesn't lose focus when using search as you type.

Steps:
1) start calibre.
2) check the preference (I normally leave it off).
3) quit calibre.
4) start calibre.
5) click in the search box.
6) type an 'a'.
7) wait a second. calibre searches for 'a'. The focus remains in the search box.
8) type 'b'.
9) wait a second. calibre searches for 'ab'

My guess is that you have configured a plugin, perhaps action chains or view manager, to do something after a search, and it is this plugin that is moving the focus.