my thought, is to include a flag on the post, alongside CW/18+ post-hiding, for third-party media. See the UI example in the image above.
This is set by the server-side HTML analysis/sanitizer engine whenever any URL is serving content (e.g., image links in CSS, SVG or <img> tags) that doesn't originate from cohost's servers by DNS match.
If there were a way to show/list which third-party servers were in the post content before opening the post, perhaps through a button in the warning header, that'd be even better.
When a post contains third-party content, it is:
- hidden by default, doesn't render, doesn't preload assets
- gives the same "show post" UI as a CW/18+ post, but with succinct privacy prose about third-party content and the user connecting directly to a third-party server, addresses or whatever
- has an option in user settings to expand these automatically; default disabled.
Just to be clear, I'm against the suggestions to disable third-party content outright, including:
- completely disable inline content embedding, let alone 3p content (this has been used in the past for extremely cool stuff, and is a big part of what keeps cohost unique)
- download and cache or re-serve images from cohost's CDN (this is, for reasons, unsustainable, and also breaks cool things done with off-server images)
- require embedded content only source from cohost's CDN - uploading to it is janky and this also breaks "cool stuff"
however, I am positively for an easier way to upload normal images to Cohost to be used, embedded or referenced inline, that doesn't involve writing a dummy draft post.
from a cursory glance at the browser devtools: cohost seems to use a tool called rehype, particularly the rehype-sanitize plugin, to preprocess and sanitize HTML as part of its markdown renderer (if the server stuff is the same shape as the local Webpack assets).
rehype has a plugin called rehype-url-inspector for analyzing and/or transforming URLs in a given input.
Attribution, Icon; Incognito by marwati from Noun Project, CC-BY 3.0.

