Three Huawei phones are banned in Taiwan, but not for the reason that you're thinking
Taiwan has halted the sale of three Huawei phones, but it has nothing to do with spying or backdoors. According to AFP, the Huawei P30, P30 Pro and Nova 5T are banned until Huawei makes a change to the operating system on the phones. The decision was made by Taiwan's National Communications Commission (NCC).
The issue that has Taiwan's regulatory agency ticked off has to do with the world time feature and the contacts page on the three aforementioned Huawei phones. The world time listing for Taiwan on the three handsets refers to the state as Taiwan, China. The same listing appears when a phone number for someone in Taiwan is saved on the contacts page.
Taiwan is known as the Republic of China (ROC) and the communist-run People's Republic of China (PRC) wants eventually to reunite the two under its "One China" policy even though both have enjoyed more than 70 years of independent rule. But Taiwan, which was last recognized by the U.S. as the one true China on December 31st, 1978, has threatened to permanently ban the three phones from the country; it simply does not consider itself to be part of the PRC. In a statement, Taiwan's NCC says, "The labeling in these phones does not reflect the facts and has even hurt the dignity of our country." The commission added that it has "taken strict measures to maintain national dignity."
The People's Republic of China does not recognize the Republic of China as being legitimate. And if a peaceful solution toward reunification is no longer possible, the PRC's official policy is to use military force if necessary to achieve this goal. But Taiwan does have its own constitution, armed forces and a president elected by the people. So to see a Chinese phone manufacturer refer to Taiwan as part of the PRC is an insult to them. Ironically, Huawei might have been responding to complaints from consumers in mainland China who have complained in the past when the manufacturer failed to refer to Taiwan, Hong Kong, and Macau as parts of China in some Chinese-language phone settings.