I can search gifs successfully on the Windows Desktop version of the application, but on the android version of the application the search function for gifs does not work. You type and it doesn't search, you tap "Done" on the keyboard and it doesn't search; there seems to be no other option.
I just tried on my Android device and GIF search works fine. Once I pressed the GIF button I can type what I want to search for -- I'm not required to press "done" or enter as search starts when I type. Pressing on one of the GIFs adds it into the conversation.