The show hasn't dealt with time travel except the one episode where that woman from the future is trying to sell the Orville to collectors in the future. Thus far they've painted a...confusing picture.
1) So in that episode, the woman from the future saves the Orville from being destroyed. She states that in her future, the Orville was destroyed, so she saves them with the intention of selling the ship. They destroy the time rift and the woman vanishes, BUT they remember her and the Orville isn't destroyed. The woman vanishing after destroying the rift would suggest linear timeline, but if she never existed, then the Orville would have been destroyed and they wouldn't have remembered her and you would have a paradox.
2) Past Kelly ends up in future. They assume linear time, send her back and we find out she does remember a bit and changes the past, which suggests time isn't linear.
It's almost like they want linear time and multiverse time combined in terms of story telling.
