For dual licensing you need the permission of all contributors. Otherwise the MIT license requires you to keep it in the repository alongside the code, since the MIT license literally says: "The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software."
AGPL is actually better for the Open Source Community. Yet, its troublesome, that license changing is treated without proper legal due diligence in my view. It could also go the other way.
IMHO, unfortunately they changed away from MIT license without asking all contributors: https://opensource.guide/legal/#:~:text=So%20if%20you're%20currently,the%20MIT%20license's%20minimal%20conditions).
For dual licensing you need the permission of all contributors. Otherwise the MIT license requires you to keep it in the repository alongside the code, since the MIT license literally says: "The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software."
That was seemingly violated in this merged PR: https://github.com/plausible/analytics/commit/84ee2c04aa0312f93cf792e1355d748cd9196d1a
AGPL is actually better for the Open Source Community. Yet, its troublesome, that license changing is treated without proper legal due diligence in my view. It could also go the other way.