There is a lot of opinion out there so I appreciate your info. I have mostly stayed away from the Tesla forums as I don't have the energy to interact with them LOL.
I've got a 2018 Tesla Model 3 LR AWD.
When we first got the car it was 289 I think. It dropped to 278 pretty quickly after we got it, and a month later settled into about 274-276. Been that way since late March. Obviously Tesla now makes it difficult to see your max charge, without actually max charging (which we almost never do). .
A 10-15 mile loss is in the range people have gotten back when recalibrating the BMS.
If you care about that enough, the procedure is roughly drain it down to 10-20%, let it sit for a few hours( usually around 4-5) with sentry mode, cabin heat protection, etc off( this allows the Tesla to sleep, thus opening the contactors). The BMS will then once the car is sleeping and after the time period will take a measurement of the power left in the battery. Then charge it up to 100% and once finished at 100%, again let it sit for a few hours. Which then the BMS will take another measurement of the power available when full. 1-3 times doing this seems to result in getting some estimated range back as the BMS has a better idea of the low end and high end of the battery.
Of course this is just what the BMS thinks is left, but your actual range doesn't change. This calibration is a peace of mind thing than anything. If the car is capable of 290 miles, it will go 290 miles even if the car thinks it is only capable of 270.