None of the upgrade tools are in a position to check architecture features before installing a package. There may not be a happy solution here.
Once you downgrade to a working version of Firefox you can use sudo apt-mark hold firefox to try to keep the updating tools from replacing it. Note that doing this will prevent you from getting security updates for Firefox. To undo this operation you can run sudo apt-mark unhold firefox Do not undertake this step lightly -- running a known-insecure webbrowser is probably a bad idea. Thanks -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1697800 Title: [regression] firefox dies with SIGILL on machines without SSE2 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/firefox/+bug/1697800/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs