The past few days (since the last larger update) when attemptiing to open the GUI for Add/Remove Software, I get the same error message as this poster from September 2024. I also read the two posts rom Nov and Dec 2024. I do not have AUR enabled or Flat Pack (or whatever it is called).
I tried pamac-manager this morning and it opened the GUI and then executed sudo pacman-mirrors --continent && sudo pacman -Syu.
Since then I had to reboot and now when I try pamac-manager, this message is returned.