Edit: I figured it out. The problem wasn’t permissions or Firefox itself, but my launcher. I’m using OLauncher, 'cause I rather like it’s text-lookup interface, but as it doesn’t make use of a traditional “home screen” Firefox won’t allow me to create an entry there.
Apparently, it’s a much-desired feature request
I think it may have been renamed to “Install” in previous versions, but neither appear anymore, and I don’t see any permissions denied so I’m assuming that can’t be it.



I wonder if it’s some kind of A/B test or something. Or they got too much negative feedback and rolled it back. I saw this UI for like a week or two on my previous phone but when I got a new device and installed FF it was back to the old UI. Not on beta or nightly channels or anything, just standard releases from Play Store.