Currently whenever we send out builds to our testers via the public install page we have to manually add their UDID to the Apple developer portal or to the Bitrise dashboard. This can be very difficult for some testers who aren’t very technically savvy and requires a lot of back and forth to get their actual UDID and then to add it to the proper provisioning profile.
I have been using BuddyBuild for some time now just because they offer this feature. When I email a build of one of our apps to a device that is not part of the provisioning profile BuddyBuild will automatically capture that users UDID, upload it to the Apple Developer portal, modify the provisioning profile and then provide a user with the build to install. You just need to link your Apple Developer account and enable this feature.
Here is a sample from BuddyBuild on what this looks like in Safari (They are handling it all in the background)