A firmware is available for the GMMK-BRN mechanical keyboard. The latest update removes the WASD/Arrow key swapping annoyance and enables the Windows Key LED light by default (instead of when it was only disabled). The firmware must be installed on a Windows machine, and make sure you disable your antivirus before proceeding.
Full changelog is available at download link below.
[Download GMMK-BRN V1.0 Update]