The whole South Coast of China was populated by ethnic groups known collectively as the Bai Yue, who were also Austronesian, and they were governed and gradually assimilated or displaced by Chinese Dynasties. I'm 90% sure that the Austronesians on Taiwan were Bai Yue or had very similar experience to them, just later.
If Taiwan is a settler colony, then most of Hainan, Guangdong and Guangxi are as well, and the coast of Jiangsu, and I'm not sure how accurate it is to call them that. Every part of China was settler-colonised by some other part of China at some point if the definition is wide enough.
Taiwan's relationship with imperialism is defined more by their post civil war political alignment than earlier migration.