suggest if /whether
I suggested if we could leave earlier.
I suggested whether we could leave earlier.
Which one is correct? Thanks.

Question

Answer

I would say neither. "I suggested that we could leave earlier" or "I suggested we leave earlier"

Answer

These forms look like "reported speech- questions".  For example if you have a question "Can we leave earlier?" then reported speech of that would be "I asked if/whether we could leave earlier".

Answer

You say "I suggested that we should leave earlier." or "I suggested that we leave earlier.".