According to Rivian their AC outlets supply 1500W max, so I guess the Stark charger's 120VAC power draw is similar to the Alta's (1400W).
I found the quote below at a Rivian forum - apparently this is from Rivian, re using one to supply house power during a blackout:
"To use the bidirectional charging feature to power your house, you can connect your Rivian vehicle to your home's electrical system.This feature allows your vehicle to store and supply power to your home when needed. You can control the charging and discharging of the vehicle's battery through the Rivian app or your touchscreen. Additional details on this bidirectional charging capability will be shared in the future."
To do this, you'd need a powerbox (one-way, vehicle-to-load) or bi-directional charger.
Below is a 3600VA (120V 30A) powerbox setup, which probably could do 240V 13-14A through a step-up device - but If I had an EV + eMC I'd look for a
higher-power EU-etc. version (@ 5-6kVA / 240V 20-25A) of this, which imo would be a damn fine solution to the bike-charging problem.