Hi,
you can set the following system properties when starting your Confluence with the SDK:
<atlassian.darkfeature.site-wide.synchrony.opt-in.disable>true</atlassian.darkfeature.site-wide.synchrony.opt-in.disable>
<atlassian.darkfeature.site-wide.shared-drafts.disable>true</atlassian.darkfeature.site-wide.shared-drafts.disable>
Put that into systemPropertyVariables or pass it with -D and collab editing is inactive after startup.
Cheers, Christoffer