I'm not familiar with this specific frame, but two of my frames came with two different grommets for the frame opening where the front derailleur cable exits. One grommet was soft rubber/silicone for Di2 cables, the other was a plastic piece that had a bolt and retention nut to keep it firmly in place. This plastic piece acts as a cable stop for mechanical shifting.
Alternatively, some front derailleurs now have a built-in cable stop, so you can run the housing all the way, e.g., Shimano 105 FD-R7000.