Better to ask questions related together within one thread. Ignoring for now the MATE/KDE questions here.
Firstly, I do understand your confusion. Unfortunately you do confuse your self more a little bit as you trying to solve something without understanding how/what to solve and also as you do mix different things together.
What is this gnome-keyring-thingy?
A couple of years ago the gnome-folks brought us their way of solving the saved credential issue.
Remember before gnome-keyring (GKR for now) all developer had to find a way to store somehow the credentials (username/password, etc), and all made it differently, secured, in plaintext, hidden etc.
GKR provides a way of store credential securely within a “encryped datasbase file”, which sometimes is simplified refered to as the “gnome keyring”. To access (store and retrieve) GKR comes with a programmable API which now developer can use.
But that was not enough, a next step was to provide a “service” API to provide access to save/restore credentials.
The service API is the part which you make accessible through the autostart entry of GKR-service.
That’s not a system-daemon/service. So no need to look there.
But there are a lot of programs out which do not care about that service anyway, but calling directly the GKR-API programatically.
And here probably starts your issue.
As you haven’t told as which programs you start, we don’t know which type of access to GKR those programs are using.
Some example: Firefox (and other firefox based browser) do not use GKR as they do have their own “keyring”
Chomium-based browser do uses directly GKR-features. Those programms which using the GKR-API using the gnome-subsystem calls to directly store (per sessions, or permanetly ) the credentials.
And you would get very often popups for those programs where you would need to enter e.g. the root password, but not always depending how those programs do call the gnome-subsystem, or of if call it et all.
To make the issue even worse for you: If you ticked in one of those first popup „Remember Password“ and „Save in keyring“ and within the next popup „Choose password for new keyring“ you changed your mind by pressing cancel. You would get always get a popup for entering and saving it into the new keyring as unfortunatly having pressed cancel did not cleared the first choice of “Save in the keyring” out of the gnome-sub-system. I.e. the (gnome-sub-) system still assumes you want to save to keyring. That’s why you might get always asked politely for a new name and password for the new keyring.
So you would need answer some questions,
as it is not clear for me what type of popup you are getting:
Let us know what programs you start and best make screenshots of the popups and do post those here
After that, we might be able to get you out of the mess.
Thats all for now.
Have a nice day.