The issue has been with the live-build prior to the Trixie release.
The function that installs the firmware prior to Trixie doesn't blacklist unneeded firmware packages depending on the architecture. So when you run the installer from the ISO it installs all firmware packages regardless of architecture.
This could have been mitigated by removing the raspi-firmware at the final stage of the installer by adding a line to preseed that instructs the installer to remove the raspi-firmware package. Basically what a user is needs to do when the error pops it's head up during an update.
On my bookworm machine instead of using the package that is in the bookworm repo I built a live-build package on bookworm using the Trixie sources. An extra line is added to the config, indicating that it's amd64 we're building an ISO for and the "blacklist function" kicks in and the raspi-firmware (and some others unrelated to amd64) are never installed when the installer is run from the ISO.
So to conclude:
It comes down to the version of live-build being used.
Bookworm version of live-build is (1:20230502), this causes the issue.
Trixie version of live-build is (1:20250505+deb13u1), this has no issues as long as --architectures amd64 is in the config file used by live build.
To install live-build (1:20250505+deb13u1) on Bookworm you need to build the package from source and install the package you just built. Also the additional line in the config file.
Building an ISO of a machine running Trixie that was successful gave me an idea as what the issue maybe. Installing the package for Trixie on Bookworm was no help, it was required to build from source.
I pretty much describe the issue in this post:
forum.linuxcnc.org/9-installing-linuxcnc...-iso?start=20#336448
