Moto G5 Plus with Square or PayPal chip reader? Square doesn't provide any compatibility information for this phone, and PayPal doesn't provide phone-specific compatibility information at all.

Does anyone have evidence that this phone works with a CHIP reader (not interested in swiping)? I suspect that the Square and PayPal Bluetooth (not earphone jack) readers work, but can't find hard evidence.
Yes, they should work with your phone.

Squire:
This device is compatible with the Moto g5 plus according to squire compatibility page

PayPal:
According to the devices compatibility page, it works with any Bluetooth enabled phone that runs Android 4.0 or higher, and has the PayPal here app.

According to Gsmarena, the Moto G5 Plus is running Android 7.0 and higher, and has Bluetooth access. 

Put the two together, and it should work.

Just double check that the PayPal here app is compatible with your phone, by finding it in the play store, and check if it allows you to download it.

Strangely, on the compatibility page it mentions that the phone has to have an earphone jack, even though this is a Bluetooth device. (But that's still not a problem being that your phone has an earphone jack anyway)