I managed to get the filters working OK by making my Prospect class conform to Comparable. I figured since name is not a guaranteed unique identifier in the context of this app, I added further logic to sort based on id.

class Prospect: Identifiable, Codable, Comparable {
    static func < (lhs: Prospect, rhs: Prospect) -> Bool {
        if lhs.name != rhs.name {
            return lhs.name < rhs.name
        } else {
            return lhs.id < rhs.id
        }
    }

    static func == (lhs: Prospect, rhs: Prospect) -> Bool {
        lhs.id == rhs.id
    }

With that in place, I updated the ProspectView to include a new computed property:

var filterProspects: [Prospect] {
        switch filter {
        case .none:
            return prospects.people
        case .contacted:
            return prospects.people.filter() { $0.isContacted }
        case .uncontacted:
            return prospects.people.filter() { !$0.isContacted }
        }
    }

    var sortedProspects: [Prospect] {
        switch sort {
        case .byName:
            return filterProspects.sorted()
        case .byDate:
            return filterProspects.sorted { lhs, rhs in
                if lhs.date != nil && rhs.date != nil && lhs.date != rhs.date {
                    return lhs.date! < rhs.date!
                } else { return lhs.id < rhs.id }
            }
        }
    }

It works, but I don't love it. My first inclination was to try to combine these two computed properties into one, possibly using dual switch statements, but I ran into a wall there.

Is there a way to accomplish what I'm going for?

Or... is there a way to add additional types of sorting within the Prospect class itself besides the required static func < ?