I'm trying to use a custom start page on new tabs opening (not happy that I have to use an extension for such basic functionality btw) but my service worker does not seem to activate or used when opening. Opening a new tab takes multiple seconds.

Navigating to the site (I have my start page hosted on AWS) on an existing tab is instantaneous, as is refreshing this page once the tab is loaded. So what gives? As far as I can tell Firefox doesn't install service workers on a per-tab basis, so there should be no issue here.