As it turned out, the problem was related so that users turned off network searches through Windows Search. So, in this case, users could observe the void when using Windows Desktop Search, and SearchUI.exe seriously loaded the processor. As a temporary solution to the problem, the developers advised to enable Bing search in Windows Search or overwrite Cortana files with older versions.
This week a full-fledged patch was released for this bug, so the “crutches” and the inclusion of the search will no longer be needed. Installing the update solves the problem. KB4515384.