Free Software for F-Droid
K-9 Mail
K-9 Mail is an open source email client focused on making it easy to chew through large volumes of email. K-9 Mail is designed for both novice and power users and offers lots of features for everyone. It provides features like Push IMAP Support, GPG & PGP/MIME support, Per Account Notifications, Unified Inbox, White and Dark Theme, and Signatures.
Manyverse
Manyverse is a social networking app that provide features like posts, likes, profiles, private messages. However, Manyverse is not like other social networks. It is not owned and operated by a single entity, instead Manyverse is a decentralized social network operated by the people. With no ads, no pay wall, no data centers, and no cookies, tracking or spying.