How to share Media library across the multi network?

I’d put all of the images in a gallery in a post and then broadcast that post, which will copy over all of the selected images.

I’d also use the Duplicate Attachments plugin to quickly copy over all of the images, and then tell Protect Child Properties to protect the attachments of the child post when updating, so that the images don’t get deleted when updating.

https://plainviewplugins.com/threewp-broadcast-premium-pack/duplicate-attachments-broadcast-plugin/

https://plainviewplugins.com/threewp-broadcast-premium-pack/protect-child-properties-broadcast-plugin/