There is a problem importing gpg keys after a fresh install of manjaro.
echo "keyserver hkp://pool.sks-keyservers.net" > /home/$USER/.gnupg/gpg.conf
is in that topic, but I remember that in the past this did work out of the box.
And because the AUR is one of the strengths of manjaro, I believe it should work without using the terminal.
Also, Pamac has the feature to give a nice dialog for adding/trusting a gpg key.
So, imo this configuration should be done at install so users just have to click a button to trust a specific key, like what is needed for installing spotify (just one of many examples)
Keep up the good work!