Hey, thank you. There is no self-hosted version as such, but there is Ilograph Desktop (https://www.ilograph.com/desktop/index.html), which is non-SaaS and works with local diagram files. You can then check your diagrams into e.g. GitHub.
A self-hosted version of what you see on web is probably a 2022 feature, after Confluence support. Real-time collaboration like Google docs is probably the same timeframe. Thanks for this feedback!