For those who missed the statement in Chinese posted before, Lai called Taiwan a sovereign country in his national security speech.
He and Tsai before him say that all the time, and the name of their 'country' changes. Variations include "this country" (Tsai's favourite), "ROC parenthesis Taiwan parenthesis", "ROC Taiwan" and "ROC in Taiwan".
Everybody on Taiwanese political talk shows recognizes that the formal name is simply ROC, and that any kind of embellishment is made-up nonsense, but they still argue over this shit endlessly.