* https://en.wikipedia.org/wiki/FreePBX
The guy who runs Crosstalk Solutions has a good YT channel on VoIP (not affiliated), amongst other tech-y stuff:
Fantastically easy to set up a PBX at home in under an hour, with no prior Asterisk experience.
When I finally wanted to ditch the GUI and get to a bare-bones Asterisk years later, the concepts carried over. The hardest part was tuning the very full-featured default config down to only the features I needed for a simple home PBX! I probably only retained 5% of the modules and config files that were default enabled