Trapped in fastboot mode with locked bootloader and corrupted custom ROM

[FPbonn]

If I connect the phone to my Computer-Display by USB-C. I can see FOS starting and get this screen:

Does it mean, that a PIN exists or something else ? I don’t have a dock available at the moment.

[FPbonn]

Some research using my Fedora VM:

$ edl modules oemunlock enable
.
.
Capstone library is missing (optional).
Keystone library is missing (optional).
Qualcomm Sahara / Firehose Client V3.62 (c) B.Kerler 2018-2024.
main - Trying with no loader given ...
main - Waiting for the device
main - Device detected :)
sahara - Protocol version: 2, Version supported: 1
main - Mode detected: sahara
sahara - 
Version 0x2
------------------------
HWID:              0x001630e100210001 (MSM_ID:0x001630e1,OEM_ID:0x0021,MODEL_ID:0x0001)
CPU detected:      "sd7250"
PK_HASH:           0x1c3d8d7ea24e435d7b540e0ffb34aa4bd57421c5f3570eef54f354610953a24c8e1930b57cc9349edaeca2466671c27f
Serial:            0x5e14XXXX

sahara
sahara - [LIB]: Couldn't find a loader for given hwid and pkhash (001630e100210001_1c3d8d7ea24e435d_[FHPRG/ENPRG].bin) :(

Already known: There is no specific loader for FP4 available. But there is also no generic loader for sd7250 (Snapdragon 750G).

Good news: No special edl-cable needed. Just press Vol+ and Vol- simultaneously and plug the USB-cable and you are in edl-Mode:

Feb 03 18:36:44 master kernel: usbserial: USB Serial support registered for Qualcomm USB modem
Feb 03 18:36:44 master kernel: qcserial 1-3:1.0: Qualcomm USB modem converter detected
Feb 03 18:36:44 master kernel: usb 1-3: Qualcomm USB modem converter now attached to ttyUSB0