This might be a bit more complicated one, so brace yourselves.
In my company we have a medium-large codebase, with 85% C#, 10% Python and the rest is C++ interop used for some C# projects.
Up until now, everything was developed in a single monorepo, single solution kind of way (~12 years of development) using subversion.
We have about 230 projects in our solution of which ~15 are applications that are distributed to our customers. Most of the rest are large, badly intertwined libraries that are basically all over the place.