A number of possibilities come to mind - most of them involving mirror problems…
A first step might be to try:
sudo pacman -Sy archlinux-keyring
before trying a rerun - This will likely make the upgrade go OK, with the possible exception of the things from the EndeavourOS repo. Then, to get the EnOS repo going, you could rebuild its mirrorlist, or as a quick ‘fix’, just comment out the first entry in the file /etc/pacman.d/endeavouros-mirrorlist by placing a # in front of it. This should allow the second entry to work, and is the ‘fast’ workaround. Or, you could regenerate the mirrorlist completely - which should drop non-working entries automatically.
I forget the command for this, as I never need to change MY EnOS mirrorlist…(I run one, so I already which to choose!) - but it should be easy to find… 