Magento 2 apply discount on tax issue + FPT

Question

Firstly I am using Magento 2.1.8 version

I'm facing an issue with tax total amount and discount from coupon code. Whenever I apply a discount coupon on the cart, tax amount stays the same. I have read a few posts saying that Magento 2 option:

My options:
Catalog Prices: Excluding tax (tried Including tax too)
Apply Customer Tax: After discount
Apply Discount On Prices Exclude tax (tried Including tax too)

Moreover, the product has FTP (Fixed product taxes) set.

Maybe someone knows this issue and have a fix for it? Also, it would be great if someone could confirm that they also facing the same issue (add discount - tax stays the same, using FPT)

Thanks for any help

Answer 1

After some more research and discussions, we got a conclusion. Apparently FPT (fixed product tax) meant to be Fixed and it doesn't change dynamically. Changing it dynamically would break it's logic. If someone disagrees - please write you own opinion to the comments below.

I have checked it with the product without FPT, only with simple tax class, taxes were changing as discount was applied.

If you still know how to apply discount on FPT product taxes, please share you knowledge, there might be people who still need to do it (sometimes clients can be demanding).