I have a different password for master encryption on boot, than for this sudo enabled user account. But this second user account does login automatically, and that is where I installed games, Chromium, etc.
First Chromium run was a while back and I reinstalled the whole system on a new disk one time at the beginning. That was because of a failed SSD. So.. frankly I can't remember if I set up any kwallet keyring stuff this time, or even specifically for Chromium. Anyway, once I got sick of the constant password pop up on run, I decided on a strong line of action and get rid of the 'little monster'. (so naive...)
But I think I now understand how it all went down:
[below story is not really pertaining to the solution of the problem. stop reading if you're short on time.]
I know my way about linux a little bit from years back, working in a datacenter. Mostly doing hardware swaps though. Back then, I made some basic scripts working. By painstakingly iterating and googling and failing and learning. And liked it. It saved me a ton of work in the end.
But without any real credentials, I'm no IT specialist or programmer or anything.
I was astounded at how easy everything worked so far with Manjaro; the whole install process, setting up Steam Games, having every bit of hardware - on either a Mac or a PC - in working order without even doing something. It was all so smooth! Later on, some minor issues I was able to work out on the spot, some I found a quick fix for by searching online. And this entire flow probably made me lazy: I pressed [Return] on a Y/n* without even reading what was there, during the process of uninstalling kwallet.
Perhaps I should have stopped, assessed, and proceeded, which I neglected to do in this case, which resulted in the eventual disintegration of my DE .
Although kwallet is back to nag me now on each Chromium run, I'm calling it a night. I will continue crafting tomorrow, and if you're interested, post here if I can get it to work smoothly with your suggestions.
Very grateful! Good night!
*) It was indeed a Y/n, not a y/N, because I do investigate those every time.