The UEFI dbx is coming through fwupd (https://archlinux.org/packages/community/x86_64/fwupd/). Discover and GNOME-Software also check for firmware updates using it.
The firmwares and related files are usually hosted on the LVFS (https://fwupd.org/).
If you run
sudo fwupdmgr get-updates
it will most likely show up too and you can do the update via the command line.
I have installed it on different distros and different mainboards without any issues. It is just a signature database for secure boot after all.
One thing to note is if you update your UEFI it might include an older database and the newer one will be overwritten and you will have to do the update again.
If you don’t use secure boot you can just ignore it.