I use TBird to access a 365 institutional ".edu" account-- at least I used to! Normally, when adding a new account or logging in to an existing account after a password update, TBird would access Microsoft online and proceed directly to the institutional site where I would enter my institutional credentials. That still works just fine on my TBird v.115 installation. With v.128, the process stops at a Microsoft online URL and pops up an authentication box requesting login credentials (see uploaded image). That is, the process halts before reaching the institutional page. Neither my Microsoft account credentials nor my institutional credentials work. Taking a look at the error log via the developer tools seems to indicates that the required functions have been deprecated.

Thanks for any insight!