I have once again switched browsers, the pendulum is now on the Firefox side. However when I changed my Emacs config to open links in firefox it didn’t work.
Instead I got the error message “Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system.”
It turned out that I had both the firefox and firefox-esr packages
installed, and browse-url-firefox tried to open iceweasel instead of
firefox. Uninstalling firefox-esr solved it.