Thanks. Will be my first EV. I have a lot to learn.I've never seen an EV that did not allow you to schedule a charge time start. One caveat - many are like the old mechanical timers for your lights, when 10PM (or whatever) rolls around, it will initiate a charge. If you plug in the vehicle at 10:15 PM, it won't start charging until 10PM the following day.
Most "smart" chargers will allow you to schedule charging as well. Some allow you to enter the time window you allow charging - typical for TOU customers (you can always override). Other connect to your utility and and gather the info to charge only at the lower cost times (once again, you can always override), and often allows them to delay charging during peak events (my utility pays me $50/yr to enable this).
I cannot see Rivian not having their EVSE set up for this - it is better for both the grid and the customer and fits with the vision put forth by Rivian. Details on how it is implemented will come in time.