Bug#861783: dpkg: trying to local divert a file diverted by a package does not work

[Joshua Hudson]

(If the suggestions below end up not being accepted, then you could
simply use your local firefox, and create a dummy package to fulfill
dependencies with something like equivs.)

Ah yes I suppose I was not clear. The firefox-esr package causes all
its depends to be installed, which is what allows the local firefox to
run; otherwise the local firefox would have a host of missing depends.