What can replace expensive Confluence?

Question

CMS

Good afternoon!
We need a documentation system for projects, with the possibility of
a) simultaneous editing of documents
b) history of changes in documents
c) commenting on documents
d) not a wiki engine
Tell me which projects you can see

Answer 1

Google Docs satisfies these conditions .

Answer 2

github

Answer 3

General approach: docs-as-code. Search the net.
Implementation: thousands of them. Choose what suits you.
But if you want to do everything in a smart way, then first you are here: How and where to store technical documentation?