[FASTBOOT][S515DL] Enter FASTBOOT Tracfone A51

Hi!

How to enter FASTBOOT mode on Tracfone A51 (SM-S515DL, FCC ID A3LSMA515U)?

Bootloader locked.

Tried all below and all failed:
1) ADB from PC - hangs on "Entering fastbook" forever
2) Choosing Bootloader in stock recovery - hangs on "Entering fastbook" forever
3) Holding both volume buttons with wire - phone does not start.

A photo/screenshot of Fastboot mode of any A51 or any Samsung phone would be helpful (I don't know how Fastboot mode looks on Samsung)

Thank you!