The real question is, the minimum fee we can pay is 1 sat, there is nothing less than 1 sat, right?
No one answered this question. The minimum fee that is less than 1 sat is zero.
That doesn't help much unless the scaling issue has been fixed at that point where zero fees ends up confirming within a day or two and people only pay fees for faster transactions.
The current minimum relay fee is 0.0001 for any transaction.
I used to send zero fee transactions, but that was 5 years ago.