The chrome://topics-internals page is now available in Chrome Canary and Chrome Dev (from version 103).
This provides handy developer information about the topics that have been selected in each epoch, and it also allows you to query the site classifier to understand the mapping of sites to topics.
Find out more:
developer.chrome.com/docs/privacy-sandbox/topics/#debug.
Improvements to the page are under consideration: add your feedback at
bugs.chromium.org.