This setup utterly destroys perf in Unreal 5.5-5.7. It works just fine in 5.4. Why?
2048 is comically huge for a cube render target, that’s 2048x6 probably in deferred generating a full set of gbuffers for every side in addition to the main view. No surprise at all that it is exhausting your GPU memory and tanking performance.
No idea why this would be any different in 5.4, can only guess that something about the setup is different or some of the default scene capture settings were changed.