[sliken]

Why not just track downloads from the mirrors? If you post a new version of package for fedora 29, just track how many downloads of that specific file are made. Write some scripts for log processing and require official mirrors to submit the logs to give you the package counts.

That way user info never makes it past the mirror (which has their IP anyways) and you don't need anything complex like UUIDs, playing tricks with NTP, or calling home.

This would give a reasonably accurate number. Use bash for measuring linux installs (pretty rare to have linux installed without bash). Then more desktop apps like firefox, eog, and xpdf to measure desktop use. If interested in server side track mongodb, apache, mysql, and similar.

This would also help fedora decide which applications they should pay more attention to.

[jewelry]

But this would be either over-counting if some CI scripts download the version every once a while, or under-counting if some organization put the image on their own privately maintained mirror which is quite common.

[noobiemcfoob]

Telemetry of any type usually fails to measure precisely the thing you want, but something adjacent that correlates strongly. What you mention are clear problems with inferring usage from downloads, but if you can infer the percentage of downloads that correlates to a machine running Fedora, you don't need much more precision.

[notduncansmith]

Perhaps packages are reinstalled too frequently to give accurate numbers? Though I agree this sounds like a good solution.