How would irrefutable evidence of extraterrestrials affect religions?

People will always believe in religion. There are many religions and just because there might be aliens, has nothing to do with religion. The term religion is a very broad term. It can even apply to atheism and global warming advocates.

ETs as in microbial life or as in a sentient being capable of rational thought and having the science and technology to be able to visit the earth?

MIcrobial life would be evidence of abiogenesis.

Sentient beings would be evidence of abiogenesis and evolution. It would certainly cause some to doubt the idea of "Human Exceptionalism."

We should learn what religion if any, the ETs believe in.

it would be another test from god to test our faith.

but it would make atheists look stupid cuz they don't think area 51 exists and they beleieve the government

edit! actually as a matter of fact, it would help christianity if they said thre was a god and / or an after life cuz they're aliens and probably smarter than us so we would have cor principles and make atheists look even dumber