FInding
A rolling ISO build for the generic flavor completes successfully, but the log contains several avoidable errors. An image build hook copies an SSH defaults file from a path that no VyOS package has shipped for years, so the copy fails on every build. The same hook creates an empty RADIUS authentication config, which the router init script deletes again on every boot. Another hook tries to disable two systemd services that no longer exist, since current strongSwan ships only a single service unit.
Separately, the accel-ppp package rebuilds its kernel module index without naming a kernel version. It therefore looks for the modules of the kernel running on the build host instead of the VyOS kernel the modules were compiled for, and aborts with an error inside the image build.
Proposed fix
Drop the obsolete copy and the two non-existent services from the hooks, and move the one remaining console log level setting into a normal configuration snippet so the hook can be removed. For accel-ppp, add a patch that passes the target kernel version to the module index update. Both hook changes were verified by a second build; the accel-ppp change still needs a package pipeline run.