Which branch of Islam has the most followers in Oman?

The Ibāḍī branch of Islam has the most followers in Oman.1

Ibāḍism is a moderate Khārijite group that is historically and ritually similar to Sunni Islam, though it differs in its emphasis on the selection of an elected imam as the community's leader rather than a hereditary one. While Ibāḍism is the predominant faith, other groups in Oman include Sunnis—primarily among the Baloch and non-Ibāḍī Arabs—and Shiʿi Muslims, who are mainly found within South Asian communities. The country's legal system also incorporates the Ibāḍī interpretation of Sharīʿah for personal status cases.124