Tusky is a lightweight client for Mastodon (https://joinmastodon.org/), a free and open-source social network server. It supports all Mastodon features, like photos, videos, lists, custom emojis and is designed according to material guidelines.
You can choose between a dark and a light theme in Tusky. It has notifications and a drafts feature.
Tusky is free and open source software licensed under the GPL-3.0. The source code is available at https://github.com/tuskyapp/Tusky