The functionality of the templates repository hasn’t changed — you can still choose a template and click the button and insert it into your instance. All that’s different is that it now lives on the website rather than in the app, and is a bit more curated.
Is there something specific you’re missing from the new version?
Pointing N8N_TEMPLATES_HOST to https://api.n8n.io/api/ should do the trick but there are some templates that may not work.
When I read your reply originally and spotted you pointed it to your base URL I made the assumption that you were using your own template service rather than ours.