Perhaps the problem is similar for very large games since there is likely large amounts of static files.
What I actually want to know is how for example, Intel manages all the different variants of a chip architecture, i.e. 1core, 2core, 4core, 6core, 8core, etc etc when there are very large amounts of similarities between them and there are very very many files not traditionally seen as source code, such as logical simulations, electrical simulations, EM interaction analysis, margin and yield results, experiments, delay files, etc etc and then layouts (potentially different variants of layouts).
I wonder if they use monorepos for each architecture variant and put differ variants into different package or is it more common for large companies to have different repos for each variants (or do they just have different github branches for different variant).