Firefox Sync is synchronizing wrong homepage URL when setup as add-on New tab page

Hello,
one of the users of my GroupSpeedDial add-on reported very interesting issue.
When you setup Firefox Sync on several devices, Firefox will synchronize homepage across them.
But if your homepage is pointing to the web-extension page, like:
moz-extension://f09107d5-c9fa-42e2-96d3-b70512b437e4/dial.html

then on different devices with the same web-extension this URL wont work - because same extension has different URL on every device…
So your home button with stop working on every device but one.

I tried to use “chrome_settings_overrides” to override homepage but seems like it’s doing same thing - just setting new full URL for homepage.

Any ideas what to do with this? Some temporal solution would be enough… I will probably create a proper bug-report as well later.

Reported and fixed in Firefox 59:

Users of ESR can exclude homepage from Sync in about:config page by setting services.sync.prefs.sync.browser.startup.homepage to false:
https://support.mozilla.org/en-US/questions/919674