On both Mac and PC, the 15.1.1 version doesn't display text frame threads.

When I create a new doc, threaded text frames DO show the threads. But when I open pre-existing documents, threads don't show at all. I've confirmed this behavior with a few other people, on both OS platforms. I'm running on Win10/64, [Version 10.0.18363.836]. The Mac users were on very recent OS's.

Allen