TL;DR There's a snapshots worlds download from Dec 2020, and we're planning on giving you the snapshots server back with a blank canvas as soon as the 1.18 snapshots arrive in the launcher and we consider them stable.
It has been over 6 months since the snapshots "chaos" server has run. It has been a long wait, and I think it's proper to explain why.
Snapshots was initially conceived as a low-stability "no promises" pure vanilla server, with no final map download to be offered. However, you the players built nice things and got quite attached to the world, so we committed to offering a final download and resolved to try to keep continuity of the world, if at all possible.
The new nether generation in 1.16 led us to consider how best to integrate new terrain generation. pez252 looked into minimising the world size by discarding chunks with only a few minutes of load time using mcaselector. But then Mojang threw us for a loop and started changing the overworld terrain generation in 1.17 snapshots. If we had run the server on those snapshots, we probably would have locked the world out of future updates, because Mojang made no guarantees about compatibility.
We also considered the effect of upgrading the current overworld to incorporate the new caves and cliffs. We concluded that the new terrain generation would produce very unsightly discontinuities (flat walls at chunk boundaries) and that we should reset the world completely when the Caves and Cliffs Update terrain generation arrives.
As you may be aware, in the last day, a new experimental 1.18 snapshot was published by Mojang. It is not yet available in the launcher. You have to download it via the link they provide. It looks awesome, but it's still somewhat tentative, so we're going to hold off on running snapshots with it until it has settled a little bit. We think that when Mojang are confident enough to offer it in the launcher it will be about ready to offer it to you. That might depend on what Mojang does about the performance. We know that 1.17 currently needs a lot more RAM than 1.16. We expect further increases on server resources in 1.18, since the world will be 50% taller.
For now, please avail yourself of the final download from last year, snapshots-1.16-2020-12-11.tar.gz (10 GB, good luck with that!). The seed we used to generate that world was "WeGotBees".