With the new update, now we only have Edge as default browser:

https://devblogs.microsoft.com/microsoft365dev/microsoft-edge-webview-for-office-add-ins/

https://docs.microsoft.com/en-us/office/dev/add-ins/concepts/browsers-used-by-office-web-add-ins

We want to have options to choose other web browser because it affects our codes and setup. We also want to be informed before any changes happen so we can give feedbacks or prepare for it. Having only Edge will make customers have the impression that we are forced to use it.