Here's what Sentient says:

Drill a hole in your seat-tube and install this squishy dropper on your Omnium.

125mm is the perfect amount of drop for the Omnium geometry, and the extra squish takes the pain out of riding your cargo bike like your trail bike or commuter.

NOTE: Drilling holes in your Omnium frame will void your warranty, but this install has been done dozens of times with no issues, so it seems worth the risk. You have been warned!

NOTE 2: Lever sold separately. The post comes with some cabling but that is it. 

Here's what KS has to say:

RAGE-iS BRINGS INNOVATION BY COMBINING A HIGH PERFORMANCE DROPPER SEAT POST WITH ADJUSTABLE SUSPENSION.

Introducing the revolutionary Rage-iS – a game-changer, entirely powered by air, that offers both drop and suspension travel. A Schrader valve nestled beneath the clamp allows you to fine-tune the spring pressure. Dial down the pressure for a plush ride over every bump. Prefer a firmer ride? Just add air. In both cases you keep full drop capabilities. Whether you’re tackling tough mountain trails on a hard tail, exploring back roads on a gravel bike, or embarking on a long trek on a touring bike the Rage-iS’ suspension system provides complete customisation according to individual preferences.