On the Firebase Analytics Dashboard they display summary data for device and OS breakdown but it does not show the complete breakdown (in my case meaning I can't view the breakdown for 44.7% of my user base). Is there anywhere in Firebase I can either view this information or export it to view it somewhere else?
It's a bit tedious, but you can add a filter on the dashboard to see the usage numbers for each device and each iOS version. Click Filters → User Property → Device Model
or Filters → User Property → OS Version
to filter to a single device or OS.
If you record or export the numbers for each device and OS, you can work out the percentage distribution.