I think there is a question of how the sundering worked, Emets Explanation in Shadowbringers used Ryne as an example, but I wonder if that was just a representation to what she did to the source. There are significant grounds to say the ancient were wiped out bar the unsundered because, no ancient remains alive in the present bar those unsundered. The closest to an ancient would be a midlander Hyur, but I suspect if Hydealyn's sundering did in fact kill everyone, then she used creation magick to recreate life afterwards, or she only spared the new life concepts the Ascians had already built and instead imbued said life with the sundered souls. We Know this is indeed possible and given that in the montage she withdrew her sword prior to sundering, I suspect she did kill all of the ancients then sundered everything and then placed those souls within the new life. Its certainly something that can be read from the montge and modern etherys.
If the ancient had indeed survived, then they should be around somewhere. We know from Elpis that some of the things they created survived until the modern day. There is the option that they were wiped out on the source and the first, but if that was so you would expect that there would be mythos and legends about them. Furthermore i think the Sundering or the final days shattered Etherys in more ways than one as Amaurot is at the bottom of the Ocean (unless of course it was a floaty Elpis like city and we know Elpis itself is still around as i think it is the islands that float above Garlemald / Sea of clouds. So if Amaurot was not a city built in the air then it means the very shape of continents/ seas changed either in the sundering or the final days. The later would make sense given Zodiark took control of the Aether rivers to weave the thick Aether shield that protected the Star. Could also be that he was also mass creating concepts to populate post saved Etherys which ended with his imprisonment and sundering.