Replacing Web Browser

I'm not at my Trisquel box right now, but I think this will do it:
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To add a new item to update-alternatives, use the following options.

Code:
update-alternatives --install /usr/bin/$LINK $PROVIDES /usr/bin/$BIN $XX

So for example... (Assuming Luajit is not available in the --config list for /usr/bin/lua)
If The link I'm updating is /usr/bin/lua, which provides lua-interpreter. I want to add Luajit, with a priority of 90, to the /usr/bin/lua link.

Code:
update-alternatives --install /usr/bin/lua lua-interpreter /usr/bin/luajit-2.0.0-beta8 90

I'm providing the correct answer so it will be available, for anyone who lands here from Google. I hate having high relevancy results, not provide the appropriate information. I'm aware this is a 3+ years old thread.

BTW, update-alternatives is a Debian family specific command. I wouldn't need to be told explicitly which distro someone uses, to address something implicitly distro specific.
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Source: https://www.linuxquestions.org/questions/linux-software-2/how-to-add-a-program-to-update-alternatives-631303/#post4544616

So you just compile an application and tell update-alternatives where it is and then set it from there so it deploys system wide. In your case the $PROVIDE will be x-www-browser.

Hope this helps. :)