OK, Admittedly I am a new user, but after installing Manjaro--KDE, and then installing Chromium all of my web browser on several different household machines appear to be hijacked by Manjaro's web page. Maybe, this was me being naive and allowing chromium to syn with my google profile, or just random chance...(try to convince me of this...really,) but seems like Manjaro is shooting itself in the foot by doing this. I mean look I doubt its invasive, but its annoying as all hell, and definitely the opposite of the experience I was looking for. I would, really, appreciate insight into why this was necessary!
It's not as nefarious as you may think. The Manjaro install sets Manjaro's website as the homepage. Reasonable, I think. But, as you say, allowing the sync made the homepage propagate. Just change the homepage back to what you want it to be, let it sync, and all should be well.
That's a Chromium problem, not a Manjaro problem. If you allow Chromium to sync and you log into your Chromium account, Google takes over.
The solution is to not log into Chromium itself, and to simply log into every website manually. It'll ask you whether it must save the passwords so that you don't have to log in manually anymore the next time, and everything will work as you'd want it.
There is no need to log into Chromium ─ Firefox has also begun pushing this thing a while ago already, but at least they're not as intrusive yet as Google is.
Uninstall the package
manjaro-browser-settings - that should do it.
But yes - if you sync your settings across devices ...
Good to know it was Google and my ignorance. Not Manjaro proper. And I already Uninstalled manjaro-browser-settings, but thanks for the knowledge all.
I still have
manjaro-browser-settings installed here ─ I didn't even know; just goes to show how unobtrusive it really is ─ and I never had your problem, so it's definitely Google's fault.