Re: Blank pages after upgrading to 1.2.3
You can change the main page under Settings–>Reading Then choose “static page” and select the page from the drop down that you want to be the home page. You might need to create a page you want to be the home page first.
If you don’t want a home page, then you’ll need to create your own theme. This page will get you started: https://codex.buddypress.org/how-to-guides/building-a-buddypress-child-theme/ but will require some knowledge of coding.