Testing old Safari browser (6.1.6) on current Linux / Ubuntu 18.04

I run Ubuntu Bionic 18.04, and I recently needed to test my website on Safari 6.1.6, released back in 2014. The closest I got was by installing an old version of the Ephiphany/Web browser, since both Epiphany and Safari are based on the Webkit browser engine.  The steps I followed, after much trial and error were:

1. Find release date of desired Safari version looking at the wiki page.  Safari 6.1.6 was released around August, 2014.
2. Find a version of the epiphany-browser package from a similar date by browsing the debian package history  If you click on the links there it'll show the date the package appeared.  epiphany-browser 3.12.1-1 is from around July, 2014.
3. Look in the Ubuntu history of the epiphany package to see if there's an Ubuntu release that has a version close to what you want.  I'm currently running Bionic, and saw the Trusty has a close version, 3.10.3-0ubuntu2.
4. Add the old Trusty repository to your /etc/apt/sources.list by adding the following lines:
   

   deb http://us.archive.ubuntu.com/ubuntu trusty universe
   deb http://us.archive.ubuntu.com/ubuntu trusty multiverse
   deb http://security.ubuntu.com/ubuntu trusty-security main
   deb http://cz.archive.ubuntu.com/ubuntu trusty main
   

5. The run some apt command to update and get the correct version.  I found the right packages to include by trial and error as the apt-get install command would fail:
   

   apt-get remove epiphany-browser epiphany-browser-data
   apt-get update
   sudo apt-get install epiphany-browser=3.10.3-0ubuntu2 epiphany-browser-data=3.10.3-0ubuntu2 libwebkit2gtk-3.0-25 libjavascriptcoregtk-3.0-0=2.4.10-0ubuntu0.14.04.1
   sudo apt-mark hold epiphany-browser epiphany-browser-data
   

And voila! epiphany-browser was available for testing / debugging.
My guess is that it's not a good idea to leave the trusty source lines in sources.list long-term since it might confuse future upgrades and may also confuse apt-cache. I plan to remove and try to cleanup once I'm done testing.