sudo add-apt-repository ppa:purplei2p/i2pd
sudo apt update
apt/
    i2pd

interesting files:
/etc/apparmor.d/usr.sbin.i2pd
/etc/default/i2pd
/etc/i2pd/i2pd.conf
/etc/i2pd/subscriptions.txt
/etc/i2pd/tunnels.conf.d/README
/etc/init.d/i2pd
/etc/logrotate.d/i2pd
/lib/systemd/system/i2pd.service
/usr/lib/tmpfiles.d/i2pd.conf
/usr/share/lintian/overrides/i2pd
/usr/share/man/man1/i2pd.1.gz
/var/lib/i2pd/certificates
/var/lib/i2pd/i2pd.conf
/var/lib/i2pd/subscriptions.txt
/var/lib/i2pd/tunnels.conf
/var/lib/i2pd/tunnels.d