I didnt count the time on my browser(firefox) in Ubuntu.
But it definitely takes most of the times more than 10sec… At least it feels like it.
On the very similar Natron forum it take also a long time to log in.
https://forum.natron.fr/
I cant test this at the moment, because I am using a live stick with Ubuntu Mate.
Everytime I start the computer, I have to copy my Bookmarks were I am already logged in.
Maybe some Firefox addons / adblock extensions take some time.