Due to the recent Pacman 6 update, Pamac (a GUI tool for Pacman) isn’t working. Pamac isn’t shipped by default on EndeavourOS but this post is here to inform new users about this upstream issue, to avoid multiple posts on the forum about this.
EndeavourOS ships with yay, an AUR wrapper that uses the command line, just read this wiki article for instructions.
As an alternative, the GUI tools Octopi and Bauh are working with the current Pacman version.