First disable the existing memcached daemon, in a belt and braces fashion

$ sudo systemctl stop memcached
$ sudo systemctl mask memcached

Create configurations for the new memcached services

$ sudo cp /etc/memcached.conf /etc/memcached_sessions.conf
$ sudo cp /etc/memcached.conf /etc/memcached_muc.conf

Edit the new configuration files so that one uses the next port up, e.g.

/etc/memcached_sessions.conf

# Default connection port is 11211
-p 11212

Create two new memcached services for our sessions and MUC

$ sudo cp /lib/systemd/system/memcached.service  /lib/systemd/system/memcached_sessions.service
$ sudo cp /lib/systemd/system/memcached.service  /lib/systemd/system/memcached_muc.service

Edit both the new services to point to the corresponding configuration file, e.g.

/lib/systemd/system/memcached_sessions.service

[Service]
ExecStart=/usr/share/memcached/scripts/systemd-memcached-wrapper /etc/memcached_sessions.conf

Enable and start the services

$ sudo systemctl enable memcached_sessions
$ sudo systemctl enable memcached_muc
$ sudo systemctl start memcached_sessions
$ sudo systemctl start memcached_muc