Grub2 configuration adjustments for bare metal

I try to build “my own” fedora core os (for bare metal) with a few adjustments in the grub2 configuration.
I somehow struggle how to do that since
cmd-buildextend-metal of coreos-assembler
uses a hard coded grub.cfg:

–grub-script /usr/lib/coreos-assembler/grub.cfg
referring to this file.

Which leads me to the conclusion that I have to build my own coreos-assembler to achieve my goal.
On the other hand, do I see in the fedora-coreos-config that certain grub.d files are dropped, which would indicate that customization to grub would be possible without building my own coreos-assembler.

Can you please help me and provide some guidance?

Yeah, we’ve been discussing moving the grub config out of cosa and into fedora-coreos-config.

Can you please help me and provide some guidance?

It depends on what exactly you want to change. If it can be done as a drop-in then that’s clearly cleaner because it’ll be easier for you to rebase on top of the latest configs. (Though would be interested to know why you’re building your own… is it just for the grub config changes or also for fun? If you have a use case that you think FCOS should support, feel free to open an RFE in the tracker: https://github.com/coreos/fedora-coreos-tracker).