I'd be a regular user in a heartbeat if there's a self-hosted version.

I regularly use a self-hosted version of draw.io / diagrams.net for creating what you're calling "multiperspective" diagrams and walkthroughs by hand - basically drawing dozens of variants of a single diagram and embedding them into docs with some text around them. I know I'm not alone, there are probably 100s of potential users in my workplace alone.

This tool can save me days/months of time but the nature of my work is confidential and I cannot use any tools that are hosted elsewhere.