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.

The sidebar on his Patreon page says

you can actually donate any amount you want per month.

On this page, you can scroll down to the bottom, and there is an option “Or choose your own price” with a “Make custom pledge” button.