jro Hi there! Welcome to the forum.
jro ( I know I can enable them, but then what's the point of Graphene ).
I assuming that "them" refers to Sandboxed Google Play here. It's absolutely your choice whether you want to use that or not, and that's why GrapheneOS doesn't come with any Google apps enabled by default.
That said, it's important to highlight two things:
While Play Services on Stock OS are problematic due to their highly privileged access over the device, the same is not the case on GrapheneOS. The Sandboxed Google Play approach makes it so they're just like any other app.
You can find more information about how it works on a high level here:
As for "what's the point of Graphene", even with Sandboxed Google Play, which already puts Play Services on an even playing field, it has a whole bunch of features that you can't find anywhere else. :)
Does elements installed directly from their github supports push notifications ?
I believe that the version that you can get from GitHub still requires Sandboxed Google Play. The F-Droid version doesn't. It would be great if they could release that version to GitHub Releases as well, or eventually to an app store like Accrescent so that people who don't want to use Play Services and F-Droid have a sensible choice.