BuddyPress.org

By default, the BP packaged theme is a child theme that uses the “bp-sn-parent” theme for the homepage, but you can always override it by copy and pasting home.php over to your child theme.

In this case, you would copy home.php from “bp-sn-parent” over to “bp-default” to override it.

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If you’re starting from scratch, I would make a copy of the “bp-default” directory, rename the folder and start experimenting.

More info here:

https://codex.buddypress.org/how-to-guides/building-a-buddypress-child-theme/

Hope I didn’t confuse you!