Android Keyboard (AOSP) can be updated to 4.4.4
Version in f-drid repo is 4.4.2, but I tried and managed to compile v4.4.4 (https://android.googlesource.com/platform/packages/inputmethods/LatinIME/+/android-4.4.4_r2.0.1). You will need inputmethodcommon
library (I used the source code from here: https://github.com/markpeak/woontua/tree/master/inputmethodcommon).
Notable features in this version: ability to choose theme.