Use Firefox ESRv52 with XUL support until June 2018 https://www.mozilla.org/en-US/firefox/organizations/ Pale Moon started a fork of the current XUL-based Firefox. Hope it will be popular. I hate XUL but a lot of people love it. I hope it will live with Pale Moon. Why would you use Vivaldi? A browser is a very personal tool, why use proprietary software for it?