Customize websocket / ddp url

i have an old app, which i now host using google cloud run. I use firebase hosting to host it under a custom domain. But this combination breaks websockets.

So my quickfix would be to make meteor connect to cloud run url directly. It’s ok, if that domain currently is visibile in the network tab.

how can i do that?

seems like this is the answer: Environment Variables | Meteor API Docs