
USBHIDKey
mikegoelzer/ESP32-Remote-USB-HID
USB dongle for remote emulation of USB HID keyboard and other server board control signals
YTLExtended
SOT-23 Bipolar (BJT) ROHS
The MMBT4124 is a bipolar made by YTL in a SOT-23 package with 3 pins. SOT-23 Bipolar (BJT) ROHS.
PCBKit's library has its footprint (Package_TO_SOT_SMD:SOT-23, from KiCad's library), ready for a KiCad board. 2,175 are in stock at JLCPCB (part C53432975). 1 open-source board in 1 repository on GitHub use it.
The library has no symbol for this part yet.
The library has no footprint for this part yet.

mikegoelzer/ESP32-Remote-USB-HID
USB dongle for remote emulation of USB HID keyboard and other server board control signals
Yes. the footprint Package_TO_SOT_SMD:SOT-23, both drawn on this page. PCBKit places them on a board for you when you design with it.
SOT-23, with 3 pins. Its footprint is drawn on this page.
JLCPCB lists it as part C53432975, with 2,175 in stock; the sellers' links on this page open their listings.
Parts like it in the library: the MMBT3904 by hongjiacheng, the S8050 by hongjiacheng, the SS8050 by hongjiacheng and the MMBT5551 by hongjiacheng. Check their datasheets: a part that fits the footprint may still differ in its ratings.
1 board in 1 repository on GitHub; the most starred are listed on this page, with their KiCad files.