alt Hacker News> Let them know. Write a letter to the CEO.
I think you're naively presuming the issue is simple and easy to address with a letter.
Regardless of your bank, payment systems such as Visa and Mastercard have blocked transactions involving mainstream online stores such as Steam because they unilaterally deemed some games to be problematic. You cannot fix this problem with an email.
These are two unrelated problems. One is "payment systems use imperfect heuristics in their own operations to fulfil their regulatory obligations." The problem I was referring to is "banks push 2FA onto end users but are unwilling to give them alternatives that don't involve meddling with the user's own most private and expensive device."
The latter is absolutely a thing where customers can (and should IMO) push back hard.