Oxide Computer published their Request for Discussion (RFD) site software [1] that they use for internal published documentation and discussion. Many are published to the public, but some are private. [2] They talk about how they use it and where it came from in their most recent podcast: RFDs: The Backbone of Oxide [3].

I suspect this would be a good 'substitute' for documents that are often hosted on internal wikis.

[1]: https://github.com/oxidecomputer/rfd-site

[2] https://rfd.shared.oxide.computer/rfd/0001

[3]: https://oxide.computer/podcasts/oxide-and-friends/2065190