Yes, the main problem is the paper with bisphenol, which has been banned in Europe.

Even though bisphenol-A is banned in EU, I believe bisphenol-B is still allowed. I suspect - though I don't know how to research whether it's true or false - that everyone just switched to bisphenol-B, which is said to be either similarly, or more toxic than BPA... :(

Even assuming that "BPA-free" paper I'd buy is really so, and not just BPA-covered one imported from China and said/labeled to be "BPA-free" by someone somewhere in the pipeline...

You need to go out of your way to buy phenol-free paper. It's a thing but unfortunately it's a niche rather than the default.

If the labeling can be trusted it isnt hard to find phenol-free receipt paper on amazon.

However, none of them say what their actual 'active ingredient' is and I am curious if these are necessarily known to be better. Most of them describe themselves as 'plastic coated'.

Yes. A short video I watched mentioned that even touching these thermal papers with normal gloves is unsafe.

The receipts that a large majority of humanity has been handling on a daily basis for decades? Unsafe? In what way?

I'm doubtful it's a majority.