https://www.theguardian.com/games/2019/oct/02/revealed-global-video-games-giants...
Steam might be tax-dodging because they own games themselfs and the law isnt enforcing it.
Viewing post in Game prices discrepancies
I believe that's related to corporation tax, not VAT. The customer pays VAT and that appears to be where this discrepancy lies.
Itch is NOT including VAT in the upfront price, Steam is - yet both upfront prices are the same, hence Itch charging 20% more in total than Steam. This is a problem I have seen more than once.