I guess this answer is about the returning of licenses? Click on “Jetzt lesen” and the web reader opens. In the upper left you can return to the overview to see all your ready to read media and there’s the option to return the book.

Wow, 2028. Well, your example isn’t even available at all here: https://www.onleihe.de/nbib24 Some libraries do send the login information with email so you could try to join a different library within a better area remotely.

Maybe there are different Onleihe services but the one I know of (onleihe.de) has multiple “copies” available, visible in the book “Infos” tab. Revoking licenses is also possible in the web reader. The revoking could be easier and it would be nice having even more licenses available for high demand items, but it isn’t nearly as bad as you’ve described.