It's weird, the log suggests subiquity is failing to install bootloader packages, the apt index refresh has errors like
Err:2 file:/cdrom noble Release
File not found - /cdrom/dists/noble/Release (2: No such file or directory)
...
E: The repository 'file:/cdrom noble Release' no longer has a Release file.
Thank you for your bug report.
It's weird, the log suggests subiquity is failing to install bootloader packages, the apt index refresh has errors like
Err:2 file:/cdrom noble Release dists/noble/ Release (2: No such file or directory)
File not found - /cdrom/
...
E: The repository 'file:/cdrom noble Release' no longer has a Release file.