Shameless but relevant plug: I built CodeApprove (https://codeapprove.com) to bring the best parts of the Critique workflow to GitHub PRs. Obviously there are many things that don't translate (Google doesn't use git, and it has insane CI/CD integration) but CodeApprove gives you the same workflow. You always know which conversations are resolved, which PRs need your attention, etc.
Feel free to reach out via email if you're curious.