Thanks for the feedback. This forum has another good resource page for themes, a visual gallery of more than 20 Discourse themes, each of which links out to demo and Github pages: Theme - Discourse Meta
Several are identified as “Official“ themes — “maintained by the Discourse team”. These could be a good choice for admins just starting out with Discourse.
“Official” themes include: Air, Avid Reader, Discourse Classic, Fakebook, Fully, Ghost, Graceful, Horizon, Material Design, Minima, Mint, Sam’s Simple, Sublime, Zeronoise.