I logged in today and was greeted with this advertisement in my notifications.
Seriously Manjaro team,
I've been happily using your OS for the past few years,
but if you jump on the enshittification train and start with pumping out advertisements in my OS,
then it won't be long before I hop to Arch...
That's just their news notification via matray, it automatically grabs anything from the Manjaro forum RSS feed or their twitter account. I don't think it's unreasonable for this to have been on twitter or their forum, and don't count it as an ad in your desktop. If you don't like it popping up (and don't care about not getting other updates in your tray from their RSS or twitter) just delete matray
I don't use majaro, but is there a store? Or a circle with a number that tells you how many updates are available? Or if you are considering switching to arch, do it the arch way: sudo pacman -Syu