Chosen Solution

OK, so I bought an international Samsung Galaxy S6 Edge off ebay and now want to swap out the motherboard to try and get better service and unlock some other options of my phone. Can I go from G925L (international/Korea) motherboard to G925F (Unlocked) motherboard? If so do I need to buy the T-Mobile daughter board to go with it?

It is possible, but the structure and layout of the motherboards may be different due to them being different variants, so they probably wouldnt fit correctly in the frame. I cannot tell you yes, but i can tell you that you can try, because i know that it is possible. I suggest that you open the phone and check it out.