Welcome to coreboot and I hope you have a lot of fun with it!
Patrick Charon wrote:
But now, I want to go deeper again, and install it on a real machine. The computer I selected is an old laptop from 2005
This isn't a great way to start - I'd suggest to select a computer known to work with coreboot rather than whatever happens to be available, and especially not to select a laptop.
Making coreboot reliably work correctly on a previously unsupported laptop requires significant effort and can take between days and years (no joke) depending on a large number of factors, some of which are out of (y)our control.
If you do want to go ahead with that hardware then please start by constructing a workable development environment, because as you anticipate the first attempt is not likely to be successful.
At a bare minimum you need a way to recover from a non-booting system, ie. an external flash programmer.
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