My device was also bricked as many users' here so be very careful if someone want to flash this ROM, in OP says to "Fix bootloop" but it has to say "To AVOID bootloop; aka BRICK" so once is done no way to follow the steps.
Luckily the files here saved my device again; the ROM and the MSM download tool was what I used to solve the brick
https://forum.xda-developers.com/oneplus-3t/how-to/unbrick-unbrick-tutorial-oneplus-3t-t3515306
If someone else is facing the same; I already had qualcomm 9008 drivers installed for all my previous Xiaomi devices that is very usual to use EDL mode with; this is the link to the drivers for 64 bit PC
https://gsmusbdrivers.com/download/qualcomm-hs-usb-qdloader-9008-driver-64-bit-windows/
My device then to install this ROM (Oreo) got bricked with no way to go to recovery either flashing all the available versions through fastboot nor hot booting to it nor flashing it directly to the boot but with a way to enter to fastboot mode that was useless anyway.
To enter to EDL mode I did power off my device using fastboot menu, the first I did is open device manager to check if device is detected and then exactly at the same time to connect device with PC it has to be pressed volume up, a yellow light is on and if PC detects it then no need to keep holding volume up button, just release it and let the tool start the operation, after all is complete you will go throw away the time to the Marshmallow era and with bootloader locked but device returning to life. Here I let you some screenshots how it looks MSM tool.
