Well, the cumulative update has arrived AT LAST (https://support.microsoft.com/en-us/help/4530684/windows-10-update-kb4530684). I have installed it and tested the search capabilities. In WinExplorer now finally it seems to be working fine.
But e.g. in the (old-fashioned) Control Panel, specifically in the section of Installed Software Applications, the return after search is not working still.
Either me hitting "x" to the right from query, or hitting "←" at the Navigation Bar -- I still have below only the specific found result, and cannot return to the list of ALL available installed things.
Dear Microsoft, is the Search a joke for you guys? 🤔