Do we redirect to ory ? if so which endpoint? which parameters. or do we send a post request from backend logout code, if so which endpoint, which parameters?

you're probably looking for this: https://www.ory.sh/docs/oauth2-oidc/oidc-logout

I've actually been studying that exact page. but t hat seems to document many ways to register urls to got to after the logout. Thats all nice, I definitely need that also, but how is that logout initiated?