My last project was about 400Gb, and probably 2M lines of C++. The days size is mostly assets but there’s still a lot of code.

Probably, but you want to version control assets too.

People usually mention git-lfs at this point, but that is always annoying to use in practice. There is also shallow-clones and sparse-checkouts, but these only mitigate the problem as there is no way around cloning at least one revision completely with git.