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One of the problems in answering is in deciding what would qualify as a Buddhist community, specifically because the word "Buddhist":
With that in mind, you could (given your apparent scholarly bent) bring the Theosophical Society -- 1875 -- into your considerations, as at least being a sangha "precursor", especially given Evan-Wentz's involvement. Clearly it was, by no stretch of the definition, what we'd call "Buddhist" today, but would even the first Buddha and his companions have thought of themselves as "Buddhist" by our contemporary definition? More likely they'd have considered themselves Hindu (although even Hindu is a term which was adopted by late 18th century Europeans to refer to the followers of Indian religions).
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I am not sure if this fits your definition but the Pali Text Society was older.
Upvote:3
There was an organization founded in 1903 in Germany:
But only to study Buddhist philosophy was for some Germans not enough. They wanted to organize themselves in Buddhist communities in order to practice Buddhism and to promote Buddhist teaching. In 1903 Karl Seidenstucker (1876-1936) founded the first German Buddhist organisation in Leipzig, called "The Buddhist Mission in Germany" and published in magazine, βThe Buddhistβ.
The paragraph before that mentions various Germans who at least studied it in the 19th century.