@ramcq shared a seemingly conservative but useful method for estimating active users:

• Look at a recent branch of the FreeDesktop SDK runtime, e.g. 23.08
• Count the number of updates to that runtime we've served between two releases

That should give us an estimate of active users, or at least active users of that runtime. For the most common runtime, it can give us a floor for an estimate of active installs, at least.

It could be nice to calculate that regularly and include it on the stats page? Open questions:

• How do we determine which branch/releases to look at?
• Can we automate that?