It was only on looking more into Linux-libre that I discovered it doesn't just remove non-free firmware, but actively refuses to load it even if you install it separately.
So I'm going with Debian - still got some more setup to do today, but not oversleeping like I usually do means I at least have a bit of time.
No point arguing that though - they'd just say having the source code means you're free to modify it, (whilst insisting immediately that doing so would be the worst thing ever).