Biblio's own Help page describes the situation thus (this is an auto translation into English):
"Why can't I use my tablet that works with Adobe Digital Editions?
We have collected information in a longer article here but in short it is due to a new EU directive coming in June 2025 that includes accessibility in e-books so that everyone can read books on their own terms. For example, the reader needs to contain support for text-to-speech / text-to-speech, and if you are visually impaired, you must be able to search for different chapters with assistive devices. Readers using the Adobe Digital Edition will not be usable after this date as the Adobe DRM that protects the files technically does not support the features required by the directive.
There is a lot of information about the new accessibility directive and you can read more at, for example,
www.mtm.se or on the government's website."
To me this is a nonsense - so long as an accessible format is also available, why should such a directive prevent people having the option to use ADE as an alternative?