Hi SueR,
Most foam mattresses (including latex) don’t have or even really need side support if they have a support core that is firm enough and the comfort layers aren’t too thick and/or soft for the person sleeping on it. There is more information about edge support with latex mattresses (or other foam mattresses) in post #3 here and in post #33 here but with a latex or latex hybrid mattress that is a suitable firmness level relative to the person sleeping on it then it normally wouldn’t be a significant issue for most people unless you often sleep or sit with most of your weight concentrated on the very outside edge of the mattress although the outside edges of a foam mattress would generally be softer than an innerspring mattress that has a specific edge support system.
The only way to know for certain whether the edges of a specific latex or other foam mattresses will be suitable for your specific body type and sleeping style or your preferences will be based on testing the mattress in person (or a mattress that is fairly similar) before a purchase or by actually sleeping on it (if you can’t test it in person before a purchase) and if you are uncertain whether you are one of the few that may “need” firmer edge support then a good return/exchange policy may be a more important part of your personal value equation just in case you are one of the few (generally in higher weight ranges) that needs or prefers a firmer edge.
I don’t know of any latex mattresses off the top of my head that have added edge support although there maybe a few that I’m not aware of or that don’t immediately come to mind.
Phoenix