To install helm, use helmenv. helmenv makes it possible to easily switch between different version of helm.
yay -S helmenv
Install latest version of helm.
# find latest version of helm in the list of all versions
helmenv list remote --all-versions
# install helm
helmenv install 3.8.0
# use the new helm (put it in path)
helmenv use 3.8.0
# test helm is setup properly
10481 helm --version