Textual words from them:
It’s our first step towards a more modern, more beautiful, and more customizable Thunderbird experience. We think you’re going to love it, and we are endlessly grateful for all of your support throughout the years 💙
All I know is that I’m in the same situation and the gmail mobile app works, so there’s something you can do.
Yeah that’s generally the goal of disabling IMAP, it just means your company is forcing you to use the official Gmail or Outlook app. It makes some sense, as if you look for email apps on the app store, you’ll see a ridiculous amount of random crap with no guarantee that they’re not spying on every email you send and receive.