Good luck, but please bear in mind complex forum posts do not get answered necessarily even same day.
I get that … both boot methods, System and Recovery fail. This will happen in the case of fastboot flashing errors; the phone is not bricked as long as we have working fastboot.
However (now of all times) you really want reliable fastboot.
Edit, let’s study the error:
fastboot: usage: unknown ‘flashing’ command get_unlocked_ability
It is a usage issue, so not specified as an “on device error”; a good sign for the device itself being OK
It is a fastboot problem where a “correct command” is seen as unknown.
It is possible that the original fail and this error is due to USB problems. Consider the whole USB chain. It has been reported that certain USB will not carry fastboot commands or complex fastboot commands. You will need a good quality (full capacity) data cable, so not a thin, skinny cable.
Avoid USB hubs including any USB hub that might be hidden in the PC / laptop.
Avoid a USB-C to USB-C cable as it may be provisioned through a hidden hub.
For predictably good results check (if necessary with a manual) that you are connecting to a USB-2 port soldered to the motherboard.
Or study of Fastboot on the PC may be productive. [HOWTO] a Safe Guide to install "IMG-e-builds" even if the /e/ web installer fails - #72 by AnotherElk