I'm not aware of a Protestant church that doesn't believe in the Trinity but Protestant merely means their lineage traces back to Catholicism and Catholicism if I remember correctly is where the doctrine was formalized.
While a particular church may require belief in the Trinity as a condition for membership, saying such belief is a requirement for salvation would be unbiblical.
Sounds like you studied theology. I should say mainline Protestants believe in The Trinity. I have a cousin who mixes Far East religions and christianty and calls herself christian, she’s not. I don’t know anything about the other religions you mentioned. I know some about mormons from FR.
There are a LOT more things that are 'required' by certain religions that are NOT biblical.
Shall we enumerate them here; or continue to point out the FALSITY of Mormonism; compared to ANY Christian (traditional) group?