Symptoms TL;DR
Installer skip Installer plugin, but pkg can be successfully installed.
Issue is that amfid refuses load install plugin because broken signature with error ELOOP.
More info
On Apple Developer Forum "Custom Installer plugin fails signature validation on macOS 27 beta 5/6" is detailed description.
Important
This is only informal report!
This is not bug in Packages.app!
We know about this issue, but it seems to be regression from Apple.
So we cannot fix it in Packages.app, until Apple fix it or informs developers, how to build package correctly.
Workaround
Move *.pkg file from connected DMG to Home or Desktop folder and launch from this location.
Symptoms TL;DR
Installer skip Installer plugin, but pkg can be successfully installed.
Issue is that amfid refuses load install plugin because broken signature with error ELOOP.
More info
On Apple Developer Forum "Custom Installer plugin fails signature validation on macOS 27 beta 5/6" is detailed description.
Important
This is only informal report!
This is not bug in Packages.app!
We know about this issue, but it seems to be regression from Apple.
So we cannot fix it in Packages.app, until Apple fix it or informs developers, how to build package correctly.
Workaround
Move *.pkg file from connected DMG to Home or Desktop folder and launch from this location.