Preparing a megathread about android FOSS apps - Part Four (Keyboards, Notes, Maps and Music Players)

This thread is ONLY to talk about Keyboards, Notes, Maps and Music Players. I add video Music Players because probably some people want to know about good FOSS alternatives.

Little context

Please, consider share your ideas and thoughts about apps on previous threads. Your opinions are really important to build final megathread. You can upvote or downvote posts so that comments gain strength and agreement between the community.