Welp, I'm spoiling some CRTs that I wish to do in the future (in another timeline) but oh well.
The big threat at the end of Milk Wars was that everything was going to get erased back into the white page, we see Rita Farr after getting crucified, ascend, and then become "in everything", keep in mind some of the usage of some words within that issue.
It is then described that high within Final Heaven, creation begins to unsew itself, implying that it exists within creation. Rita, ascending and becoming literally one with all of creation, in the scan directly after that, sees the Eonymous creating the young animal universe after gaining this omnipresence, if she can see everything and become everything, she embodies the world of the Eonymous as well. And thus, both Final Heaven and the Eonymous are within "creation", which Rita embodies.
Rita then sits on top of the panels, describes herself as one with everything, and reboots existence.
If all of that is simply just not as dangerous as the destruction of the DCUs metacontinuity, then the DCU continuity takes precedence over practically everything meta within Milk Wars, and thus, everything, including the Eonymous, are within the DCU metanarrative.
Simply enough, this "meta" business kinda doesn't exist past Limbo, so I think both Rita Farr, the Eonymous and Final Heaven are around that level as well.