When configuring a Mixpanel Lexicon publishing integration, you'll now see a new toggle that will enable you to publish your tracking plan to the Lexicon EU Data Residency API, rather than the global API.
Previously if you had a Mixpanel project configured for the EU Data Residency, you would have gotten a 404 error as the project would not have been found in the global API. If that was your case, you can now head over to your Avo Publishing screen, flip the switch on your Mixpanel integration and it should publish successfully.