[FBISurveillance]

See https://app.diagrams.net/ -- you'll recognize the style.

[m463]

so that seems to be: https://github.com/jgraph/drawio

[INTPenis]

I use the same service, but I always knew it as draw.io. Never noticed when they started redirecting to this domain.

This is very valuable to me as a Linux user in a Microsoft Platinum partner org because I can't run Visio natively.