I found this, and I understand that even if you contribute through eNPS, there will still be some POP (in this case SBI) fee per transaction and on an annual basis.
But thanks for your suggestion. I will try to make a small transaction to test it.
This is the note from the eNPS portal:
POP Trail commission will be applied to the contribution amount @ 0.10% (subject to a minimum of $10 and a maximum of ₹10,000 per transaction). This fee will not be applied to subscribers registered with eNPS through Aadhaar.
So, by investing from this instead of SBI directly, the charge rate drops from 0.25% to 0.10%, but remains positive. So if someone knows if a switch is possible, that would be great.