What theducks said is correct:
Quote:
Originally Posted by bino
calibre, version 3.21.0
...
InvalidPlugin: The plugin at /tmp/calibre_3.21.0_tmp_ah2O5i/8G5WGe.zip needs a version of calibre >= 3.48.0
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See
https://calibre-ebook.com/download for newer versions of Calibre.