Voultar just uploaded an open source RGB bypass design for Sega Genesis consoles. At the moment, a full bypass is the only way to guarantee a jailbar-free solution on all models of the Genesis.
UPDATE: If you lift the RGB pins, you need to restore the pullups: https://www.retrorgb.com/fix-for-all-rgb-bypassed-sega-genesis.html
A stupid simple (DC Coupled) Sega Genesis RGB bypass apparatus. Buffers everything (including C-Sync) – Designed to work with all Genesis C-Sync SHART cables (regardless if there's a resistor on the C-Sync line or not)
— Voultar (@Voultar) July 2, 2018