Hi Pavel,
I think you need a compile step before you deploy to Firebase Hosting - Firebase Hosting performs no server-side operations on the files in the directory you upload, so if you only upload an index.jade file, it will literally only serve up an index.jade file.
Assuming this was your firebase.json:
{
"firebase": "your-firebase-app",
"public": "public"
...
}
You could try `jade public --out dist` before deploying, which will compile the templates into a 'dist' folder. If you change your firebase.json to:
{
"firebase": "your-firebase-app",
"public": "dist"
...
}
Then you can run `firebase deploy` and you should see the content you expect
Hope that helps
Chris