An Indonesian court found seven Papuan men guilty of treason in a high-profile trial closely watched as an indicator of political freedoms in the world’s third-largest democracy.

The Balikpapan district court sentenced Papuan activist Buchtar Tabuni, a senior figure in the United Liberation Movement for West Papua (ULMWP), to 11 months in prison. Prosecutors had called for Tabuni to be jailed for 17 years...