Thanks. The Companion app never seemed to work on my sandboxed Google Play profile on GrapheneOS however. I’ve since found Golden Cheetah which is a native Linux program and totally free. Zwift raising their price was the final straw for me to move on and I’m grateful for it.

GC works perfectly on Linux Mint with my Garmin USB ANT+ dongle, Garmin heart rate strap, and retains all the functionality with my Zwift Hub trainer if anyone is curious.