@caitlin Thanks for that, and to the devs. I have installed my Mudcat addon in Nightly.
I wanted to install this but I can’t add it to my collection: https://addons.mozilla.org/en-GB/android/addon/android_new_tabs_in_foreground ‘Find an addon to include in this collection’ doesn’t find it. Paradoxically I suspect that’s because it’s in AMO as an Android addon - not available for the desktop platform. I suspect that’s unintentional.