Quote from A1 Computers on January 13, 2023, 12:27 pm

The first decision to make is if you will host your PBX locally or in the
cloud, things to consider:
Bandwidth, number of extensions in a call group,
Video conferencing and expected call volume.

The cloud is most resilient
when the you have bandwidth limitations, however in a larger ring group
scenario; hosting locally can may be necessary.

3CX offers and .ISO image
ready for production and takes about 15 mins to install, probably another 15
mins for you to configure the default options.
You could also make use of an
existing computer and install it on Windows, you may want to take advantage of
Windows Server Active Directory or a quick and easy integration of contacts and
internal company services including Outlook integration.

3CX makes it so
simple you almost need no instructions since the interface will guide you
through the entire installation process.

Get The .ISO or Windows Installer 

Installation on Debian 10:

This method is no longer supported by 3CX.  This method should be for
testing and not for a production environment

Code:

wget -O- http://downloads-global.3cx.com/downloads/3cxpbx/public.key | sudo apt-key add -
echo "deb http://downloads-global.3cx.com/downloads/debian buster main" | sudo tee /etc/apt/sources.list.d/3cxpbx.list
echo "deb http://downloads-global.3cx.com/downloads/debian buster-testing main" | sudo tee /etc/apt/sources.list.d/3cxpbx-testing.list
sudo apt update
sudo apt install net-tools dphys-swapfile
sudo apt install 3cxpbx