useless research for the curious
Did a bit more research, was thinking it might be a systemd service, so I checked for timers there, but there was just a countme timer enabled that basically tells the server to include you in the count of active systems (how to disable, for the paranoid 🥸).
Then I went on to look at the live logs of rpm-ostree and, as found from this website used this command:
journalctl --follow --unit rpm-ostreed.service
So that I could monitor its activity while I open Discover and so I managed to record when it happens, I also saw from the logs that there is a configuration file at this path /etc/rpm-ostreed.confand that you can configure automatic updates from there, by default there a this line about it (usage greatly explained with man rpm-ostreed.conf btw):
[Daemon]
#AutomaticUpdatePolicy=none
but it's commented out, so it couldn't have been that.
Finally there is this one thing that pops up in the logs:
Initiated txn AutomaticUpdateTrigger for client(id:cli dbus:1.1625 unit:app-org.kde.discover@df0f43f8979843c0a34d36ad199c7eda.service uid:1000): /org/projectatomic/rpmostree1/fedora
So it is something triggered by Discover, as I had known already, due to other articles that talk about the integration with Discover, but I wasn't so sure about it anymore, since I couldn't find any related settings in the app.
So I found the setting that configures automatic updates in general... in the three dot menu (questionable UX decision?):
which actually just leads to the system settings:
I had this configured to be weekly, there isn't even a setting as granular as seconds, the smallest span of time is daily, but what I'm guessing is that the "Update frequency" acts on when they should be installed automatically rather than when they should be fetched, so this is a limitation of the system as I understand it