You're arguing about something I'm not. The fact the waveform collapse appears instant doesn't violate causality at all. To break causality the collapse should be usable for communication, but it isn't.

Yet it does appear instant, from all data we have. And that is not explained at all by our current understanding of quantum physics. It's "explained" as in we observe it, and can calculate how it works. But it's not explained as in how come that collapse happens instantly regardless of the distance.

Therefore spacetime is either non-local, or we need another interpretation like many worlds that avoids the collapse and replaced it with neverending waveform, or something else.

To say there's nothing here left to explain to me says you don't understand the problem in the first place. Either that, or you know something that leading physicists don't know right now.