What is the best and right way to open-source packages from a company monorepo?

There are a few tools to split commits from sub-dirs to a branch which you can then push to a public repo/monorepo.

E.g. `git subtree`, https://github.com/facebook/fbshipit, https://github.com/splitsh/lite, https://github.com/ingydotnet/git-subrepo.

A lot of these approaches though rely on the source-of-truth being the internal company monorepo. PRs are synced internally, merged, and then pushed out. It means that someone outside the organization cannot be a maintainer, and the speed of PR merges is dictated by the available resources inside the company. So I'd argue this is not the right OSS way of doing things.

Even if there are two public monorepos out in the open you can have similar problems trying to collaborate, because to modify one line of a package, you may need to pull a huge monorepo and its tooling down.

Does anyone have a solution or an example of an OSS-friendly approach to monorepo open-sourcing?