On top of that, ostree does deduplication based on file checksum. So if different packages ship the same binary, it will be only one copy on the disk and again, the mmaped regions will be shared among processes.

It's not easy to share libraries across containers, unless they can be built to share a base layer in a stacked union filesystem approach.

Well, in my original post (GGGP) I've defined "a library" as "a .so file" so what I can say is that the 872 distinct .so files used on my laptop will be shared among the different processes that use them.

If you assume the same library can be duplicated in two different .so files, then 872 is just an upper bound on the number of distinct libraries and further sharing could be done.

Eitherway, that is a significant amount of code sharing, which was the original question in this thread.

If the containerised versions of apps all have different versions of dependencies (quite likely IMO as they'll have the freedom to), there won't be any sharing.