I'm using Fabric and Fastlane to deploy my beta builds to testers. Currently, when I have a new tester, I invite them via email, and they go through the Fabric onboarding process. Then, on all future builds, they'll receive a message "The developer needs to add the device's UDID to a build." So then I go to developer.apple.com and add their UDID to my provisioning profile, and they can run the next build. It works as desired.
Is there any way within Fabric/Fastlane to automate this process of adding UDIDs to the provisioning profile on deployment? It seems sigh within Fastlane can manage provisioning profiles, and Fabric obviously has access to the device UDIDs, but I can't find any documentation about this particular step.
Check out the docs on how you can use fastlane to automatically add device testers to your profile: https://docs.fastlane.tools/getting-started/ios/beta-deployment/#best-practices
There is currently no automatic integration with Fabric Beta, you'll have to manually add it to your list of devices. It's definitely something that can be improved.