Do you know what the cost of an even moderately new FXO/FXS gateway is?
I just posted about this here:
How to define a pj_sip trunk to a Cisco ISR4321 - FreePBX / Endpoints - FreePBX Community Forums
You don’t need CUBE licensing. In fact you don’t even need an ISR4321 a ISR2800 will do.
Put ISR4321 4FXO into Ebay and you will get dozens of the following for under $100 such as this one:
Cisco ISR 4321 Gigabit Integrated Service Router IPBase 1xNIM-4FXO ISR4321/K9 #2 | eBay
You can get 2 of them one as a spare.
They are tanks and will run forever no matter how many updates to FreePBX and Debian you do.
And best of all that let’s you virtualize FreePBX on HyperV or KVM/QEMU or ESXi whatever your preferred hypervisor is.
This is truly one of the biggest reasons to go to an external gateway is it uncouples the dependency from specific hardware and operating system to FreePBX.
And if you want to know I am also very sympathetic to orphaned hardware. But the idea of plugging a phone line into a card that plugs into the server you’re running your PBX on is just faulty. Server hardware changes faster than most people change their underwear and it makes the one thing more complex which is a hinderance to troubleshooting.