Yup, that’s what I use. In the svg-icons field, enter users, user-friends and whatever symbol you want to use for public access (for the globe, I’m using an icon by Freepik, which I’ve added to my Discourse via a sprite uploaded to a theme component)
I hide the lock icon with this CSS added to a theme component:
// no lock icon for private categories
.category .badge-category.clear-badge.restricted .d-icon-lock,
.badge-category.clear-badge.restricted .d-icon-lock,
.category-list .category-text-title .d-icon-lock,
.category-box-heading .d-icon-lock {
display:none;
}