While waiting for reply, I tried updating mirrors and then resetting the gpg database like suggested here: Can't update software - Keys missing from Keyring - #5 by cfinnberg
And using pamac update which also deals with the issues explained here: [Stable Update] 2021-06-14 - Kernels, Browsers, Mesa, Deepin, Systemd, Gnome Apps 40.2, Pipewire, Haskell - #2 by philm
Now it seems to be running…
I will update if is succeeds.
Update: It succeeded.