That's good news. Could someone do me a favour and try this test OPDS library
https://cops-demo.slucas.fr/feed.php
When I try it in the PocketBook Reader android app, it fails to open for example Authors->D->Doyle, Artur Conan. It for some reason opens a browser page showing the XML instead. But it can open Authors->W->Wells, H. G. and the War of the Worlds epub fine.
Wondering if it's the same on an actual PocketBook. If it is then I'll see what I need to change to the COPS feed to get PocketBook to be able to read COPS Calibre OPDS feeds.