If you use nostr:npub12vkcxr0luzwp8e673v29eqjhrr7p9vqq8asav85swaepclllj09sylpugg, you can see a count under the Explore tab. This is what it looks like right now, 753,026. Don't know if it's accurate or how it is calculated.
Discussion
But the public keys created were not created by users? Should those be counted, or not? 753,026 is small amount user
Would be a good question for nostr:npub12vkcxr0luzwp8e673v29eqjhrr7p9vqq8asav85swaepclllj09sylpugg