[DNSB]

Originally Posted by PiperKev

The author pushed a fixed version that now works with calibre 5.38.0.

https://github.com/steinarb/opds-reader

I've already picked up that one. After realizing that I'd look at the wrong version, I went to the 2nd Google search result. Sadly, the version from there still gives the following:

Spoiler:

calibre, version 5.38.0
ERROR: Unhandled exception: <b>KeyError</b>:'server'

calibre 5.38 [64bit]  embedded-python: True is64bit: True
Windows-10-10.0.22000 Windows ('64bit', 'WindowsPE')
('Windows', '10', '10.0.22000')
Python 3.8.5
Windows: ('10', '10.0.22000', '', 'Multiprocessor Free')
Interface language: None
Successfully initialized third party plugins: DeACSM (0, 0, 15) && DeDRM (10, 0, 2) && Annotations (1, 16, 0) && Baen (1, 2, 0) && Barnes & Noble (1, 2, 16) && Calibre Power Search Plugin (2, 1, 2) && Count Pages (1, 11, 2) && Diaps Editing Toolbag (0, 3, 7) && EpubCheck (0, 2, 4) && EpubMerge (2, 12, 0) && EpubSplit (3, 2, 0) && FanFicFare (4, 10, 0) && Fantastic Fiction (1, 5, 1) && Find Duplicates (1, 9, 4) && Goodreads (1, 5, 3) && Goodreads Sync (1, 15, 1) && Hyphenate This! (0, 1, 3) && ISFDB (3, 0, 0) && Job Spy (1, 0, 190) && KePub Output (3, 5, 3) && Kindle hi-res covers (0, 5, 0) && KindleUnpack - The Plugin (0, 83, 1) && Kobo Books (1, 8, 4) && Kobo Utilities (2, 15, 1) && KoboTouchExtended (3, 5, 4) && Modify ePub (1, 7, 0) && OPDS Client (1, 0, 0) && Obok DeDRM (10, 0, 0) && Open With (1, 7, 0) && Quality Check (1, 12, 1) && Resize Cover (1, 1, 0) && ScrambleEbook (0, 4, 5) && SmartEject (2, 4, 0) && Smashwords Metadata (1, 0, 2)
Traceback (most recent call last):
  File "calibre_plugins.opds_client.ui", line 24, in show_dialog
  File "calibre_plugins.opds_client.main", line 68, in __init__
  File "calibre_plugins.opds_client.model", line 78, in downloadOpdsRootCatalog
KeyError: 'server'