Once upon a time, before Android 6.0, one could access its dictionary directly and add words to it. This seems to be working again! I had created this list of Maltese words (from resources on http://mlrs.research.um.edu.mt/) to add to my phone's dictionary (using https://play.google.com/store/apps/details?id=com.usr.dict.mgr&hl=en or other means), such that then whenever I wrote a word with Maltese-specific letters (e.g. tiegħi) I could write without these (e.g. tieghi) and Android keyboard would immediately suggest the correct alternative (i.e. tiegħi). In this way I avoided introducing a new keyboard with Maltese characters while writing syntactically correct Maltese, but alas that is no longer possible.

Note: "wordlist.txt" should have no repeated words, while "otherwordlist.txt" has many repetitions.