Most other posts are correct including the reference to the TR blog post - calories burned calculated as an estimate from power is far more accurate than HR based estimates or height/weight/distance calculations. Some apps used to provide an estimate purely on distance (ignoring work completely).
Imagine coasting down a hill for 10 miles casually without putting any power. You really don’t burn any calories outside of metabolic losses, but a simple calculation of height/weight/distance would possibly claim a 500 calorie burn. This is a contrived extreme example but just tries to get the point across. It’s not even a criticism of the other sites, they have too little information to give very accurate results.
I think any training app / power meter / garmin or wahoo bike computer will show you very consistent calorie estimates when used with a power meter and they will be very close to the TR number.