Overwrite meta og:image image source to use externally public loaded images on topics?

Do you mean my discourse doesn’t have permission to access S3 Bucket of other 3rd party free CDN images sites?
If i can access an image in a browser, then discourse can too, and already discourse is optimising the images i share using hot-links. So i think we need this feature for sure.

i updated my reply above for discourse CDN comparison, please check.

What other cheapest way do you suggest me to host my images in bulk? Because i am afriad that if my site get millions of topics means billions of images, and my Discourse site backup will start getting bigger bigger and very hard and expensive to manage/scale and migrate. What would i do in that case then?