(dnf, yum, AL2023)

dnf is now the preferred way to install software on AL2023.
E.g. dnf install <package-name>

ls -l $(which yum) shows that yum is symlinked to the dnf-3 executable.
All the commands I use below still work.

(yum, list repos)

sudo yum repolist all

(yum, repo conf file location, al2023)

/etc/yum.repos.d/

(yum, dnf, conf file location, al2023)

/etc/dnf/dnf.conf

(yum, see enabled repos)

yum repolist enabled

(yum, enable repo, disable repo, al2023)

dnf config-manager --set-enabled <repo-name>
dnf config-manager --set-disabled <repo-name>

(yum list installed, list installed with wildcard)

yum list installed
or
yum list installed "mysql*"

(yum uninstall package, remove package)

yum remove <package-name>

(yum, see installed files by package)

rpm -ql <package-name>

(yum, list available packages)

yum list available "maria*" --enablerepo=<some-repo>
or
yum list | grep -i maria

(yum, gpg keys location, al2023, amazon linux)

/etc/pki/rpm-gpg

(yum, al2023, amazon linux, epel does not work)

It seems epel is no longer compatible with Amazon Linux 2023.
Posted on twitter here: https://twitter.com/louzell_/status/1668062601308413954
If someone figures it out please let me know.
It used to be possible to modify /etc/yum.repos.d/epel.repo and set enabled to 1, but that file no longer exists.