I'm glad someone has looked into but it doesn't confirm or deny much. They were -measuring mortality- against those already infected and those "instituionalized but asymptomatic". It doesn't seem to say anything about making symptoms milder for those that contracted covid-19 after taking supplements or for those who have already contracted, which is what I think OP was suggesting.

How do you get to that conclusion from that paper?

All I see from that paper is that there is "no evidence" that Vitamin D is beneficial with COVID-19 (and some qualified evidence that it may help other respiratory infections).

They mentions several planned/registered studies on the question, but none that have reported results yet.

That’s calling out a lack of formal trials providing evidence, not discrediting the data that is emerging.

Either way, they still recommend supplementing if deficient(which the numbers for people with IVD are quite high in most regions).