I have found a workaround to remove an old accounts from your Microsoft Authenticator app on an Android.
If you have an android mobile, follow the instructions below:
- Open your mobiles' Settings, then tap on Users & accounts or Accounts and backup (depends on the android version).
- Scroll down and look for Microsoft old account(s) you want to remove or Work account and tap on it.
- Once you found the required account, tap on it and select More or tap on 2 dots : (depends on the android version) in the upper right corner of your screen.
- Select Remove account. You may need to repeat it twice or thrice.
- Once account has removed, close the Microsoft Authenticator app if already opened.
- Now tap and hold on Microsoft Authenticator app, and select App info.
- Select Storage usage > Under Cache, tap on Clear cache.
- Open Microsoft Authenticator app, and old account(s) should not appear now.