Hi (sorry for my english 
)
So, if you look here : a configurable product in a developping website
When you choose an option, the price including tax change to price excluding tax.
All is ok in the cart.
All is ok for simple products.
Test a lot of tax configuration and other but no changing.
Could you help please ?
Magento 2.3.1 (test with magento 2.3.2 and 2.3.4)