Well, someone claims it works with FreePBX 15 at any rate:
Issues with FreePBX 16 — FOP2 Forum
But, it’s clear from THIS thread:
Migrating FreePBX with FOP2 to new hardware - FreePBX / Hardware - FreePBX Community Forums
that FOP2 has pretty much completely abandoned it’s web forum support forum, and 100% of the activity/support now is on that Telegram channel they talk about in the thread.
This post really underlines that:
Is FOP2 / Asternic still in business? — FOP2 Forum
So, get on the Telegram channel, ask your question, and please report back here and update this thread.
It DOES sound like a one-man shop though and my guess is that he’s swamped with support work from a few large customers with many virtual cloud PBXes.
I have used FOSS (not FreePBX, however, that I only ever used for myself) for years with clients when I was consulting - the rule of thumb though with using FOSS for clients is to test test test on your own stuff first.
I run around 6 different Virtual Machines on 2 different Ubuntu Server systems running KVM-qemu that are FreePBX instances, just for testing only.