I am using a listed “dumb” trainer (Tacx Blue Motion) and a bluetooth combo speed and cadence sensor, connected to Zwift via Mobile Link app.
In Settings / Virtual Power Mode, zPower option is disabled. Is it because I am using bluetooth, not ANT+?
zPower is disabled because your trainer isn’t a zPower trainer. You can read up on the difference between zPower and virtual power, as well as what trainers support both, in our supported trainer article.