I had an old Engin ATA - a Sipura SPA-2000 - which I had unlocked from Engin but due to the weird firmware Engin installs I only had access to Line 2. I decided I wanted both lines so I did some more research to see if anyone has had any luck luck getting done lines free. And lo and behold in the world’s longest Whirlpool thread on the topic someone had. It involves replacing the Sipura firmware with Linksys PAP2 firmware. And it worked perfectly. Very impressed with a very clever solution.