The only way to solve this is to have the user of the credit/debit card pay the fee. Sure, you can do an EU thing of 0.2-0.3% or whatever it is, but this might still be 0.2-0.3% more than it could be in a competitive market.
Perhaps forcing everyone to just implement free payments between any bank accounts, like pix, is actually the only viable solution here (and i just accept that this is one of those market failure things).
I wonder if true transaction cost even reaches the 0.2-0.3% or could be further lowered.