Apparently perma.cc is officially used by some courts in the US. I did use it in addition to the wayback machine when I collected paper trail for a minor retail dispute, but I did not have to use it.

I don't know how exactly it achieves being "legally certifiable", at least to the point that courts are trusting it. Signing and timestamping with independent transparency logs would be reasonable.

https://perma.cc/sign-up/courts