Some Custom TRRS cables from way back in time : r/Kriscables
Mechanical Keyboards 101 - BrainDo
Custom TRRS Cable for Split Mechanical Keyboards - Canada
TRRS Cable – Keebio
TRRS Split Keyboard Cable - Unicorn Cables
Build Your Own: TRRS Split keyboard cable
custom TRRS cable – Keebstuff Kabelmanufaktur
Plenum 3.5mm TRRS Male to Male Cable White - Installation Grade
Custom TRRS Cable for Split Mechanical Keyboards
Kriscables, Lisbon
Cathay Photo Deity Smart Cable TRS to TRRS