Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Based on my research, I found a related Microsoft Q&A discussion that includes guidance for Android devices, which may be helpful for reference: How to remove an old account from authenticator app - Microsoft Q&A
To remove the account completely, you may try removing it from the device settings and refreshing the app state:
Open Settings on your Samsung device.
Look for one of the following menus. The exact name may vary depending on your Android version: "Passwords, passkeys & accounts", "Accounts", "Accounts and backup", "Accounts & sync"
Look for the old work or school account and, if it is present, remove it from there.
Restart the device and then check whether the account still appears in Microsoft Authenticator.
If the account is associated with an Android Work Profile, you may also need to remove the Work Profile from the device settings.
Additionally, if the same account is still configured in Microsoft apps such as Outlook, Teams, OneDrive, or Microsoft 365, please sign out of those apps first, as they may continue to retain and re-surface the account.
If the account does not exist in Android account settings, no Work Profile is present, and the Remove account option remains unavailable in Microsoft Authenticator, I was unable to find any documented method to remove only that specific account entry. In that scenario, after ensuring your remaining Authenticator accounts are backed up or synchronized, reinstalling the Authenticator app may be the only available workaround.
I hope this helps.