Admittedly I have not synced Firefox in years, but definitely after 2010, which seems to be a date Firefox has said will be to far back. In fact it was probably 2015 sometime.
The bad part is, I cannot even Import as HTML backup from Chrome, or anything for that matter. I cannot Browse to any Folders to do so at all from the Bookmarks Tool in Firefox. I could Import from Chrome as soon as I get it installed, but would like to be able to Import as HTML also.
Also, I cannot ask questions on their site, even though I am logged into Sync, getting all my Passwords and can see all my devices from previous Sync's.
I don't expect things to be perfect, especially since they have gone through so many changes recently, but would like to be able to at least log in to the Forums to ask questions. I thought if I were logged into Sync that qualified me to log onto the forum and ask questions?