Is the officiant also going to be part of the reception?

It might say in their contract...my officiant says they will be leaving after the ceremony because they have a life outside of doing weddings

It is usually customary to invite the officiant and their spouse. More times than not, they will decline attending.

If the officiant is a friend or relative, definitely. If they’re just hired, it’s still customary to invite them but they don’t always come. I would ask them directly during your planning because some officiants will definitely not want to come and then you don’t have to think about it again. If they say they don’t want to come, I’d still offer a meal if they want one.