Adminer is in the repos, so install it with:
apt install adminerCopy the configuration to your available configs folder and enable it.
cp /etc/adminer/apache.conf /etc/apache2/conf-available/adminer.conf
a2enconf adminerReload Apache.
systemctl reload apache2I rather enjoy @pepa-linha's Adminer Design Dark theme as an alternative to the default theme. Download it to the Adminer folder with:
curl https://raw.githubusercontent.com/pepa-linha/Adminer-Design-Dark/master/adminer.css > /usr/share/adminer/adminer/adminer.css

YOU DESERVE A BEER!