There are a couple of ways how you can do that in Bugfender:
Option 1: Use enable/disable features to send information only from certain devices
While your devices are in disabled state, the logs will be written in the device anyway, just not sent to Bugfender for collection. When you enable a device, logs will be sent to Bugfender, including the most recent logs that were written in the device.
If you need to obtain user consent, you use device associated data to identify individual devices to enable, and even you can include the user consent itself (for example, with a value such as data.collection.allowed = true/false or similar).
Option 2: Completely disable Bugfender from certain devices
You might want the Bugfender SDK not to collect any kind of information nor to contact the Bugfender servers. In this case, you can choose not to initialize the Bugfender SDK when your application starts.