BuddyPress.org

Naming your child theme “default” doesn’t do anything… just name it the way you want to name it.

eg. /wp-content/themes/my-theme/

View Andrea’s post just a few posts above you to set your new child theme as default for new blogs. This only works for new blogs.

If you want to set a new theme for all existing blogs, you’ll need to run a custom script to change every single blog to the new theme.