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.
Lucki
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.
16 available licenses
Revoking licenses in the web reader
I see you have the G502 in your current list: Make sure you get the X variant as those are using optical switches. I believe piper still needs a beta build to have the mouse included.
I'm still not sure that filter thing is necessary. FreshRSS can fetch content and images using the CSS selector of the website. You may want to check out the Advanced section in their documentation: https://freshrss.github.io/FreshRSS/en/users/04_Subscriptions.html#retrieve-a-truncated-feed-from-within-freshrss
Anyway, whatever works for you :)
Well, it's the same AI supported translation running locally, so I very much expect it rivaling the online service.
What's the extension for? FreshRSS can fetch contents natively.
Sadly the translations are shit and even worse than the infamous Google translator. Nothing comes even close to DeepL. At least it's local though.
FYI: Falls man Tesseract als Frontend nutzt, kann man dort auch in den Einstellungen ohne Werbeblockerumweg filtern.
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.