I think someone has done similar. https://support.mozilla.org/en-US/questions/1303378

I saw that question, but it was a little vague. The answer to that question seems to be about searching for an address, which isn't the problem I'm having. The answer also suggests: "If the problem is that some other mapping site is coming up that you do not want, one possible culprit would be an extension." None of my extensions seem to be at issue, It turns out it's the link itself, which I am ashamed to admit I did not see until just now. https://maps.apple.com/?address=451+Galvez+Ave.%2C+Hunters+Point For some reason, the website uses Apple Maps, rather than Google Maps. I suspect that is their preference for mobile users. No way to force Firefox to over-ride that. Problem not solved, but understood.