Is Confucianism an ethnic religion like Zoroastrianism and to a lesser extent Judaism? Buddhism, though perhaps not as eager to proselytize as Christianity or Islam, was open to converts throughout nearly all of its history. Buddhist monks helped spread the faith. If I recall, Confucianism was mainly introduced into Sinicized people, essentially the Chinese and peoples under Chinese rule or hegemony for various times. The Koreans, Mongols, Hmong, Vietnamese, and maybe the Khmer and Lao. As an exception the Japanese adopted Confucianism at some point though they were not under Chinese rule, though Japan is considered part of the Sinosphere. I do not think that Thailand or Burma were ever Confucian (but then the latter two nations were as much part of the Indosphere as the Sinosphere).