Separate communities of genetically and linguistically distinct communities that domesticated plants and animals independently, but also in parallel with each other. Europe and the Near East also went through a similar situation.
Independent language phyla during the Early Neolithic in China (cf. Vovin, Robbeets, etc.):
Amuric = Nivkh
Koreanic
Old Liaodong = "Japanic" ("pre-Japonic" in the Liaodong and Korean Peninsulas)
Old Liaoxi = phylum that influenced Altaic via agricultural vocabulary, etc., but is not Altaic itself
Old Zhongyuan = "pre-Sinitic" ("isolate" substratum in Sinitic)
Old Shandong = "para-Austronesian"; very genetically and archaeologically distinct from Old Lower Yangtze; thus, likely a separate phylum unrelated to Old Lower Yangtze
Old Lower Yangtze (OLY) = "pre-Austronesian"
Old Middle Yangtze (OMY) = "pre-Hmong-Mien"
Old Lingnan = "pre-Austroasiatic"
Old Upper Yangtze = early Sino-Tibetan
Old Xiangxi = "pre-Tujia" ("isolate" substratum in Tujia)
Siangic
Migrations into China during the Bronze and Iron Ages (cf. Vovin, Robbeets, etc.):
Turkic
Mongolic
Tungusic
Yeniseian
Ruanruan
Indo-European (Tocharian)
(Note that I do not consider Altaic to be a true family, but rather a linguistic area, much like how the five language phyla of East Asia form a linguistic area.)
That's 18 phyla total during the Early Neolithic. There were likely even more.
Today, in China we have only 8 phyla:
Sino-Tibetan
Kra-Dai
Hmong-Mien
Austroasiatic
Turkic
Mongolic
Tungusic
Koreanic