Hoping the group can clarify some things for Uber/Lyft drivers (of which I am one), and I'll communicate the information in the taxes section of the Uber drivers forum.
1) If you have a vehicle used exclusively for TNC (Transportation Network Company) use, can you still use the standard mileage deduction?
If you want to use the actual expenses rule, what is the maximum cost basis for depreciation and is the depreciation straight-line over the depreciation period? Is it 3 years? If you use the vehicle partly for business and partly personal, do you pro-rate the depreciation? Only a small number of Uber drivers would probably want to do this, because it's way more record-keeping. However, some who have expensive vehicles and are driving "Uber Select" might.
2) What expenses can you deduct other than the mileage?
I assume you could deduct:
Non-vehicle equipment necessary, such as a bluetooth headset, perhaps your smartphone if you could show the phone was not also for personal use (unlikely), business cards, water, candy etc. given to passengers.
Can you deduct cleaning? Obviously only money paid to third parties, not the "value" of your time for cleaning the car. I'm thinking most specifically like if someone pukes in your car and you get it professionally cleaned. (This is one of the occupational hazards.)
What about insurance? And what if your personal policy cost, say, $500 a year but it went up to $1000 a year when you changed the coverage to include ridesharing?
3) I assume that the mileage deduction is based on miles driven between 12:0AM January 1 and 11:59PM on December 31, but the income is based on what Uber pays you during the calendar year. In other words, you have the minor but common mismatch of miles driven the last few days of the year for which you're not paid until early the next year.