Show discount including tax, calculate discount excluding tax

Question

I want to display the discount amount including tax on cart overview page (totals summary).

• Magento 2.1.8

Relevant settings:

• Catalog prices: Excluding tax
• Apply Customer Tax: After discount
• Apply Discount On Prices: Excluding tax

Current situation in total summary within cart:

I cannot set Apply Discount On Prices to Including Tax, because Magento then calculates wrong totals. So in short I need to calculate discount amounts excluding tax but displaying including tax.