I think the best example (although it's not a digital platform, and the ownership is for the benefit of employees rather than customers) I know of would be the

I think the best example (although it's not a digital platform, and the ownership is for the benefit of employees rather than customers) I know of would be the John Lewis Partnership in the UK. It's incorporated as a public limited company, but all of its shares are owned in trust. https://en.wikipedia.org/wiki/John_Lewis_Partnership https://en.wikipedia.org/wiki/John_Lewis_Partnership