Using Classic Outlook on Windows for personal email, calendar, and contact management
I just woke up to this annoying App Search bar as well. This is pathetic. Also, the "Show Apps in Outlook" checkbox is no where to be found in File-->Options-->Advanced. I have Outlook 2016. It appears it was update 2401 published on January 30, 2024 that caused my problem. Updates are described at this link:
Please Microsoft, republish an update to fix this fast. Stop trying to fix what isn't broken. If I did such things in my job, I would be terminated.