I found that for no clear reason that I was receiving the following error trying to deploy to my iPhone 6 plus device, using iOS 12.1.
AMDeviceSecureInstallApplicationBundle returned: 0xe8008015
This I've found is an indication that your device is not in your provisioning profile, or your provisioning profile is invalid.
First issue - Invalid provisioning profile
After checking my profile at https://developer.apple.com/account/ios/profile/limited it actually had an invalid status next to it. Even though it had not expired. At this point I re-created it, and downloaded it to the mac and installed it.
Second issue - Multiple provisioning profiles
Visual Studio was set to Automatically determine the appropriate provisioning profile. As I had a few, I came to the conclusion it was using the wrong one. Probably a good idea for me to delete the unneeded ones, however I instead just set the bundle signing to "Manual", then chose the profile I thought was valid.
This allowed the app to then be deployed successfully to my device.