Nothing crypto specifically solves as a user.
> Nothing specifically solved
Besides permissionless transactions? Does your credit card offer those?
Do you pay monthly fees for the privilege of not paying fees on foreign transactions? I do :(
Which single currency satisfies the GP's description?
No fees on any credit cards I keep, except 1 which was waived this year when i called to change it to a free card.
If irreversible transactions worry you, use an intermediary; the way you already use credit instead of cash (which requires no permissions).
Any single currency?