The “video memory has been exhausted” error, I think is quite literally what it sounds like: you have no more free VRAM, and your GPU is maxed out.
I’ve found that even with all “new” features disabled (lumen, nanite, virtual shadow maps, temporal super sampling, etc.) UE5 EA consumes significantly more VRAM (3+GB) than older versions of the engine even on completely blank projects.
What’s more is that, if you populate a map with a lot of expensive assets and then delete them all and re-start the engine…that empty level will also consume more VRAM than a level that had not been populated at all (even though both are identical in their contents). Perhaps there’s a technical reason for this that is beyond me (as I’m an artist, not a programmer).