Is the slogan of Taoism "immortal Buddha" or "immortal happiness"?

It is infinitely longevity. Taoism is not called Buddha.

There is no boundless Buddha in Taoism, or I say three boundless, all of them drift with the tide and have no idea what the source is. The three infinity here are: unlimited vision, unlimited life and unlimited happiness. The origin of "three boundless" is very early. Later, because there was an infinite Buddha in Buddhism, which was homophonic with the infinite happiness of Taoism, Taoism was changed to "infinite Buddha" in order to distinguish it. Infinite buddhas mean many buddhas. The infinite Buddha can't be used alone, but only with several others. Because there is no such thing as "boundless Buddha" in Taoism, it should be called "boundless Buddha"

The word of Taoism was originally "infinite longevity and happiness", which is a special term for blessing honesty, and is not the same as "Amitabha" in Buddhism. However, the word "Fu" in Taoism is pronounced the same as the word "Buddha" in the southwest dialect of China. In order to avoid misinterpreting people's confusion between "infinite longevity Buddha" and "infinite longevity blessing" in tantric Buddhism, later Taoism unified the whole country to regard "blessing as the supreme Buddha" as an eternal sacred name.