Version 2.5.1 has a weird way of opening the first local ZIM file from the list "Local Files" after starting the application (tested on Windows 10 and Debian 12):
The application seems to restart itself; the window disappears and then reappears. When I open another local ZIM file after that, the window stays the same. Version 2.4.1 doesn't have this behavior, so it seems to be a regression.