Richard Feynman's report on the Challenger Disaster[1] was so divergent from the desired political posture they made it a separate appendix. It stands as a showcase of root cause analysis.

[1] https://web.archive.org/web/20001018100729/http://science.ks...

The only ones that stand out in my mind are the Cloudflare post-mortems: https://blog.cloudflare.com/tag/postmortem/

They are impressive both in the depth at which they talk about the issue, and also in the speed at which they get published.

Roblox one is one of my favourite: https://blog.roblox.com/2022/01/roblox-return-to-service-10-....

FWIW - my company https://rootly.com/ builds a tool that helps automate postmortem write ups (e.g. timeline creation, etc).