Should still work on older Hardare. I believe they are phasing out support with V7R1. There are a number od 3rd Party Hardware devices that change twinax dumb terminals to Lan Connected dumb terminal still using twinax wiring.
Check BosNova and TwinData devices
IBM i is becoming more and more a partition hosted on a Power System. The leading OS on the Power Systems seems to be AIX and slowly but steadily we see typical AS/400 hardware replaced by Open Systems hardware at a much lower cost.
Take in addition the functionalities that are not covered by IBM i directly, but by installing a VIOS and …… you see it is time to move forward.
Dumb terminals are the kind of things that physically almost never die, but as everything around does …… we replaced them by 10Zig (Bosanova) Linux based terminals. The replacement was seamless and almost no maintenance required. In the worst places (dusty industrial environment) we also added the dumb terminal like keyboard. They come at a cost, but are made by the same manufacturer as the ones for the IBM terminals and they last forever.
When looking at the bill in the end …… by removing the SNA support on the routers provided by our WAN provider, we saved more than what we invested.