Despite your having found a solution that works for you Clive (I love it when old hardware comes to the rescue), I thought I would chime in and say that Zwift is mostly working for me on a Samsung Galaxy Tab S6 Lite with 64Gb. The graphics are plenty snappy.
I say “mostly working” because I am having a problem when I minimize the Zwift app to go watch a movie on Netflix or YouTube instead of staring at the Zwift UI full-time. The elapsed timer and other data logging freezes at the time when I minimized the app, and I don’t get credit for kilometers ridden. Oddly, though, the elapsed time in that particular segment of my workout does continue ticking along. But this is an issue for another post.