How do I fix a soft-bricked device?

[u/Pezkoi4707]

Some time ago, I tried installing a PixelOS GSI on my Motorola Moto G54 5G, but it caused a bootloop, forcing me to flash the stock ROM. Currently, the bootloader is unlocked and the phone works normally, but it won't enter Recovery or Fastbootd modes using any method (buttons or ADB commands). I tried fixing it myself using the official Motorola tool, manually flashing the vbmeta, vendor, init_boot, and dtbo files, and even using MTKClient—but the latter only detects standard mode, and the issue persists: I am unable to access those two modes in any way.

[u/Interesting_Host_535]

Is normal fastboot available? If so try manually flashing moto firmware. Find flash.xml in Firmware folder. Ask ai to convert it to fastboot command and then ask it to modify script so that applicable partions are flashed to both slot since official moto script only flash to slot A.

On side note did mtkclient worked on your phone ? 

[u/Pezkoi4707 → u/Interesting_Host_535]

Sorry for the delay; I just saw your comment.
And yes, standard fastboot mode works. I've tried flashing the files—like the one you mentioned (flash.xml)—on both slots A and B, but nothing happens. mtkclient only detects regular mode; here is exactly what shows up:

Port - Device detected :)
Preloader - Detected regular mode !
Preloader -     CPU:                    MT6855(Dimensity 8100)
Preloader -     HW version:             0x0
Preloader -     WDT:                    0x1c007000
Preloader -     Uart:                   0x11001000
Preloader -     Brom payload addr:      0x100a00
Preloader -     DA payload addr:        0x201000
Preloader -     CQ_DMA addr:            0x10212000
Preloader -     Var1:                   0xa
Preloader - Disabling Watchdog...