Nothing prevents anyone from taking all of the bits and pieces, Debian, FreePBX and so on, and packaging it up as a single VM
I’ve thought about doing this for a while and am seriously considering doing it soon with FreePBX 17, Debian 12, Asterisk 22, Chan_sip, the Cisco USECALLMANAGER patch, and the Cisco Provisioning Server targeted as a drop in replacement for Cisco UCMs. Then releasing it as both a KVM vm image and a HyperV image.
The biggest problem you run into when doing this is proving it out on various hypervisors and hardware combos. Producing the VM is easy. Producing documentation for using it is more complex, but it’s not impossible, and even doing support on a freely available product (like for example FreePBX 16’s ISO) is not hard since there’s no contractual requirement to support all of the border cases. This is after all what Incredible PBX does but IMHO they overload it with hylafax, and the vpn and routing crap, which IMHO is either dinosaur tech (honestly, fax, in 2024???) that is better offloaded to a real higher end fax machine, or better offloaded to a hardware router, or openwrt box.
But the big problem is I don’t have 2,000 desk phones somewhere handy with 2,000 bodies making phone calls that could be used to push the thing to it’s limits on the hypervisor/hardware. With Switchvox/Starvox/PBXact they are selling licenses to specific limits which pretty much flatly states will support X number of phones - so if a business with X number of phones goes and buys one of those machines and the licensing for it - it’s guaranteed to work (or it’s fraudulently sold, obviously) with that number of warm bodies.
And then of course, there’s the deskphone support issue because phones require firmware loads which are copyrighted. Somehow, 3CX.com and firewall.cx seem to get away with distributing firmware versions of really old, antique Cisco phones without getting takedown notices from Cisco - but they both lack some key phone firmware files that are required to update older SCCP loaded phones to SIP. I wish I knew how they got away with it, maybe just the fact that they only have firmware for EOL phones available gets them out of the Cisco radar.