Dropped my absentee ballot off at an official drop box 2 weeks ago. It took a week for the county to acknowledge receipt and another couple days for them to accept it (in California you can track your ballot's progress).
I have had them reject my ballot in the past due to my signature not matching the one they had one file (it has become a bit of an unintelligible scribble over the years) so I made sure to go slower and clearly delineate each letter.
My mother mailed her ballot the day after I dropped mine off in person and hers was accepted & counted within 3 days so they were clearly focusing more on processing mailed ballots than dropped off ones.