How about with multiple repos, across multiple systems? Eg. embedded device with 4-week test cycles, backend server with CI/CD, frontend site with CI/CD, and up

How about with multiple repos, across multiple systems? Eg. embedded device with 4-week test cycles, backend server with CI/CD, frontend site with CI/CD, and upstream vendor contribution PR(s), and where the data fees for firmware updates to the set of all customer embedded devices run into the hundreds of thousands of dollars? You can't get them all in one commit then. Even with a monorepo (not contributing back to upstream) it'd be an utterly massive commit.