This chapter explores digital sovereignty claims in Brazilian activism on Mastodon, the most relevant development of federated social media. The free and open source software (FOSS) movement has always advanced digital sovereignty discourses, emphasizing bottom-up struggle for control and autonomy over technology. Federated social media are the open source response to the rise of corporate digital platforms and their proprietary business model. However, most narratives about FOSS struggles, including Mastodon, emerge from the core of the global capitalism. The specific appropriations of digital sovereignty discourses by Mastodon activists in the Global South and, in particular, in the BRICS are still understudied. This is even more relevant because of the history of technological sovereignty in the global periphery, in which bottom-up activism has been much closer to the state than in most FOSS narratives. Drawing on participant observation, interviews, and country data, the chapter contributes a nuanced understanding of how Brazilian activists articulate and shape digital sovereignty discourses. It finds out that Brazilian activism represents a step toward the politicization of the FOSS movement, but still attaches little value to the geopolitical dimension of social media struggles, departing from the historical contribution of FOSS activism in the Global South.