I now use Obtanium[1] for my open source android apps, it grabs apks straight from the source (github, gitlab etc.). Once you get each app set up its a breeze and you don't have to deal with fdroids strangeness.
I'm not sure Facebook and a now Facebook owned platform are good examples for private communications. There was an article posted here a week or two ago detailing how Facebook sold access to the contents of users private messages to advertisers.