As of 11/2021, this is bleeding edge development. You need to switch to devel repositories which may break your system. To do that place deb https://maedevu.maemo.org/leste beowulf-devel main contrib non-free into /etc/apt/sources.list and run sudo apt update.
Voice calls should be working, or close to working, on Motorola Droid 4. Ofonod is handling the modem, and it is configured and running by default. Modem is not enabled by default. enable-modem and online-modem scripts from ofono/test can be used to put modem online. sphone can be used as an UI to place and receive calls, it can be installed using sudo apt install sphone.