Here, the developer explained why development activity decreased:
While it is true that due to private reasons I had to take a bit of a pause of developing FlorisBoard and some time passed with no progress at all, implementing a completely new statistical NLP (Natural Language Processing) provider, or in laymans terms the long-awaited word prediction and spell-checking implementation, is also a huge task which takes a lot of time and trial-error and development time.
For my phone (almost 7 years old), a thin needle to scrape out all the dust is sufficient. Pressurized air also helps.