The fact that no one knows anything for sure doesn't ipso facto mean it's anything but the simplest, most obvious truth: Harry and Meghan had a baby and the baby looks like both of them and perfectly healthy, there was no surrogate, the legal implications in Britain would have made it more trouble than it's worth to hide when she obviously was able to do it on her own.
We already know most of the family cannot stand her, especially William and Andrew, so all William's expression says is what we all expected: "I'm taking one for the side otherwise I wouldn't be here."
The Harkle shitshow has nothing to do with DNA, surrogates, or conspiracies. The only things it has to do with are an angry spoilt confused younger brother who found a woman who could make him feel that he was entitled to be just as important as Big Bro and with her help, that's what he could be. She just happened to forget that the people whose permission and status she needs to pull it off have the money without which she can't turn herself and Harry into Bill and Melinda Gates or George and Amal Clooney. Gates and Clooney made their own money, but Harry has to turn to Papa and Gran for his, and there they are, fobbed off with that third-rate official residence, no real base in one of the starriest hoppin' capitals in the world, and the UK press that they so unwisely threatened at Meghan's urging before they were even engaged are now running a vicious PR war against them. And, they're being booted out of the UK as far as is decently possible to leave the home turf to the far more important Cambridges, who now look golden thanks to Harry's and Meghan's really staggering ability to turn gold into straw.
That's all it is. The secrecy nonesense is Meghan playing the only role she really does well: Drama Queen, using Harry's resentful persona as the engine.
They alienated the UK press before they were even engaged, started alienating the Queen before the wedding even took place, alienated the rest of the family in the ensuing months, particularly William and Andrew, and like all narcissistic paranoids, they're now blaming everyone (including the Cambridges and the UK press) for their woes, instead of themselves.
There's no surrogate, there's not DS baby, although I wouldn't be at all surprised if recreational drugs of varied kinds weren't part of their home entertainment system.
They probably can't wait to leave the UK, and the BRF probably can't wait to see them go.
That's really all there is to this story.