Huh got no idea why all the files got nuked, weird.
https://archive.org/details/xbox-sdks should have pretty much everything that was there, if you notice anything missing let me know and I'll try checking if I still have it anywhere.
BTW a small request, last year over christmas some big things leaked out, mostly X360/Xbone things, but in all the confusion there were also two extremely early alpha-kit ISOs released (earlier than anything on that archive.org link IIRC) - I had them downloaded, but then foolishly deleted them when I needed to clear space, assuming the link for them would stay up, sadly the link was removed due to the boring non-XboxOG stuff though ;_;
Well it's been 10+ months since then and I still haven't seen them reappear anywhere, if anyone knows the ISOs I'm talking about it'd be great if you could upload them, really hope someone out there managed to save them...
(E: I think XDK_RECOVERY_OCT/XboxSDKOCT2000 were the filenames for one version, pretty sure there was another version leaked too - if anyone has these an upload would be appreciated!)