The antennas that came with the MD380 aren’t very good, and are really just a dummy load, and are cheap plastic.
My MD380 came with two antennas. A shorter one, and a longer one. Both worked okay for receiving, but left a little to be desired in quality. When I swapped between the two, I noticed metal shavings being left behind on the radio’s connector, and then they wouldn’t screw in as easily.
I found the Smiley Antenna Slim Line 440MHZ antenna via reddit, and purchased it. It’s tuned specifically to 440MHz which is at most 5mhz off from the DMR repeaters output frequency in my area.