I had never head of Rive before and it looks like something I can use in one of my projects. Thanks, this is the kind of stuff that keeps me addicted to HN.
https://rive.app/blog/introducing-vector-feathering
I do understand the appeal for an open format though. Rive seems to have their own proprietary (documented) binary format: https://rive.app/docs/runtimes/advanced-topic/format
Then I downloaded the app and found you can't use it without setting up an "account" and being online.
So in the end, this is more tiresome Web-only crap. Deleted.