Is Taiwanese a Minnan language?

That's right, because the ancestors of most people in Taiwan Province Province immigrated from Zhangzhou and Quanzhou, Fujian Province, they extended their mother tongue (Minnan dialect) to speak.

Although there are many Hakkas and people from provinces other than Fujian in Taiwan Province Province, Zhangzhou and Quanzhou in Fujian account for the majority.

Therefore, it is popular to talk in Minnan, and even Hakkas and people from provinces outside Fujian have naturally learned Minnan because of their integration into society. Over time, they used to call Minnan dialect Taiwan Province people.

There are two dialects in Minnan dialect: Zhangzhou accent and Quanzhou accent, which have evolved into the unique Minnan accent in Taiwan Province province over time, so the pronunciation is slightly different.