Check UniFi device count from network.unifi.ui.com
First, enable Remote Access under Settings > Remote Access and link your user to your account.ui.com login.
Then, log in at unifi.network.ui.com. You’ll see the total device count in the Devices column.
Alternatively, you can check UniFi device count from SSH: https://tran-technology.com/check-unifi-device-count-from-ssh