The case of the lost and found ring
I've thought since before the season even started that Kyle and Amanda split long before they claim they did, and definitely before summer, but now I'm sure of it. I also think most of them already knew it and were playing along.
In the first dinner of the season, Amanda takes a shot at Kyle about losing his ring. It had little to do with the conversation but there was a mention of them cosplaying as single. Seemingly out of nowhere she makes a comment about how Kyle lost his ring so she is refusing to wear her's until he finds it. He seems so annoyed at this and the first time I watched it I barely caught it because they spent the whole dinner bickering anyway. After a second watch I don't think he was annoyed because she was taking yet another shot at him but because she came up with that on her own to explain their missing rings and just had to make him the bad guy for being the ring loser.
Later in the season, at that SB soft launch, Kyle's ring miraculously returns to his finger yet Amanda's doesn't. No mention of him finding it and no mention of her ring still missing from her finger (not the biggest deal).
I usually don't think much of people not wearing rings, it happens. It's more about how she brought it up and seemed like she was giving a preemptive excuse to a question no one asked.
Combined with the rumors of a separation that started way back when, West raising her hand when the question was asked about who was single, the coverup comment about cosplaying single, and them not riding together all summer I think it's obvious they were already separated when summer started.