Smartphone Keyboards: The Achilles Heel of Data Privacy
medium.com
medium.com
Also, 200M installs does not equate to 200M users (affected).
FOSS keyboards which don't need internet permission are available on Fdroid:
AnySoftKeyboard
Simple Keyboard
OpenBoard
Indic Keyboard
Hacker's Keyboard
Though you can get away with firewall-ing any app you don't want connecting to the internet using apps such as netguard or afwall+.
Open source keyboards you've mentioned are probably your best bet if privacy is your main concern.
To perform network operations in your application, your manifest must include the following permissions:
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
source: https://developer.android.com/training/basics/network-ops/co...