You answered it yourself, ETA is the word, right ?
You also said it has a unit, and the unit is minutes.
So I'd say the correct variable name should include the unit as well as what the unit represents. Not just what it is in terms of types of things (duration, timedelta, etc) but what it represents specifically:
etaMinutes
minutesUntilETA minutesUntilArrival
minutesUntilNextBus
At least that's what I was taught in school, that longer variable/function names like this are generally better. Textbook was https://picopublish.sequentialread.com/files/cleancode.pdf
I think I largely agree with that book to this day 🤓