@
stanking - there's this
Usage Statistics for calibre - I don't know if Kovid has more granular stats - ie which versions of Windows, OS/X and Linux.
You could install 1.48 (portable if you have Windows) and do some tests against it. If your PI works you could make that the minimum version that would allow the folks stuck on older versions of XP & OS/X - I imagine they'd give you some brownie points for that.
But its inevitable that one day you'll have pull the plug on compatibility with old versions and change the minimum.
That said, given you're developing new PI's it would be more than reasonable for you to set the minimum calibre version to the one current at the time of the initial release of the PI.
There's nothing to stop a user changing
minimum_calibre_version in
__init__.py to there current version of calibre and trying. Most PI's don't change too often.
BR