How can I rely on a spiritual witness that the church is true, when people in other religions obtain similar witnesses that their own church is true?

The "world" has identified feelings - frisson, elevation, ASMR, flow - which seem awfully similar to how I've felt the Spirit

This is because the "world" has co-opted what religious people have understood for a long, long time.

I'm not sure why that should delegitimize it.

And then there are people who belong to other faiths, who relate having spiritual feelings and experiences that seem just as powerful to them as mine are to me.

Mormonism doesn't claim exclusivity to spiritual manifestations. In fact, it creates a requirement for its members to seek truth outside its institutions. This is because the Holy Spirit testifies of truth wherever truth is taught/shared.

What does that mean - is the Spirit testifying to them that their religion is true?

The Holy Ghost testifies about truth in instances and over time. This is why every scripture (that have been cited here) explains that we can "know" principles (or behaviors) experientially. In other words, we can know something is truth by practicing it over a period of time. This means lots of people outside of Mormonism who practice faith, charity, repentance, etc have testimonies.

The challenge here is that people index truth to institutions. The Savior warned Jospeh Smith about this during the first vision. He condemned institutional creeds - not people or practices. This is why the Savior gave the great commission, which is why the church fields over 100,000 missionaries, you know?

They speak about their feelings, how they "just know" that it is true! And it sounds just like testimony meeting!!!

I'm unfamiliar with the film you're citing (I don't care to see it - I don't need that in my life, you probably don't either). I would imagine if we could talk to those poor people, they were entranced by how the organization talked about true principles that were conflated with false ones. This is how the Adversary rolls.

historical evidence

Historical's a problematic word.

The only positive evidence that can't be explained away is my spiritual witness

This is what Moroni was talking about in Moroni 10:3. You and God enter a room. What happens there is between you and him.

We're all in this with you.

/r/latterdaysaints Thread