I use Firefox as primary browser, but use Gmail in Chrome.
I'd like all the links in e-mails and chat to open in a new Firefox tab instead of a new Chrome tab, automatically (I know copy-paste, drag and drop… !).
I looked for an extension, or an userscript. I didn't find any, and I'm not even sure an userscript in Chrome (with Tapermonkey) can send an open-link event to Firefox.