Emoji viewer constantly popping up in input fields
Solution 1:
Yes, this is super annoying!!! This worked for me on my 2020 M1 Macbook Air running Big Sur 11.2:
On certain Macs, pushing the FN key (which may have a "globe" it) can bring up an emoji keyboard. Disabling this shortcut can be accomplished by opening the System Preferences and navigating to the Keyboard panel.
From within the Keyboard tab, look for the label that reads Press "globe icon" to. It likely reads "Show Emoji & Symbols". Click on the dropdown and choose Do Nothing to disable the emoji shortcut.
Found this on https://appsliced.co/ask/how-do-i-disable-the-emoji-keyboard-shortcut-on-my-mac
Solution 2:
I faced the same annoying bug with emoji viewer in macOS Mojave (10.14.6).
Possible solution
In case of multiple input sources, try to delete one of them (System Preferences -> Keyboard -> Input sources) and add deleted one again. System restart was not required in my case.
If you have only one default input source, try to add some another and then delete it.
I hope this solution comes in handy