I wanted something to make it easier to download books directly from my Pocketbook reader.
I tried enabling the built in OPDS support. I couldn't get it to authenticate to me Calibre-Web server, I suppose it was disabled for a reason.
I just so happened I had to subscribe to Gemini Pro for work so decided to do something more useful than work during my trial
So after a couple weeks vibe coding I have built a native OPDS client using the C SDK.
It’s just a single .app file you drop into the device's applications folder via USB. It will then create the directory it needs in the application folder to store configuration and cache. It connects directly to OPDS servers (like Calibre-Web, or Project Gutenberg) and downloads the files straight to your storage. It supports pretty much all the native formats.
I mainly built it to fix a few annoyances I had with browsing on an e-reader. It has a search feature and It has the option to show thumbnails or not in the catalog views, it caches book covers locally so it doesn't hammer the server, and reverses the screen where you tap something so you aren't left wondering if the device registered your touch.
If anyone else finds this useful, the source code and the compiled release are up here:
https://github.com/j2robin/Pocketbook-OPDSClient
I tried to make it as robust as possible but have only been able to test it on Pocketbook Era and Inkpad Color 3. I did make the UI scale proportionally to whatever resolution the device reports but haven't been able to test on anything like the verse or older readers.
I hope it proves useful to you as well.
Let me know if you run into any weird bugs with your specific setups.