Not offhand, but perhaps this is something you'd be interested in sponsoring?
Reach out to us at [email protected] 🙂
This plugin replaces any image url using http with https. However, if the image host is not secure, the image will simply not show.
nodebb-plugin-camo is a secure proxy server. It converts http image urls and serves them through the proxy. This means that even if the original image host is not secure, the image will still appear.