This would also work.Why is this the case? Is this inability particular to the version of the factory build that you have installed? Where is the failure? Are the dev options not available, or does adb over usb just not connect?
Since your device is exploitable and unlocked, have you considered installing fred's boot-from-usb ubuntu build?
Fred's ubuntu build preceded the unlock method release, and at the time of its release would have been of no use for a situation like yours because any attempt to modify the emmc system from the temporarily usb-booted system would cause avb to fail.
But since your device is unlocked and exploitable, you could use the temporarily usb-booted ubuntu system to dd a factory recovery image back to the emmc, and avb wouldn't be an issue. Fred's method also enables aml v2 factory burn via the reset button, which could give you another vector to write the recovery partition using the update utility via burn mode. The same methods could also be used to write a magisk-patched boot image to the boot partition.
Using an update command with burn mode may also provide a method to instantaneously boot to bootloader fastboot, without even rebooting the device.
The only issue you may run into when trying to do this is that the bootloader version may be stale relative to the bootloader that is currently installed on your device, so the bootloader used, or fred's method of disabling anti-rollback detection may need to be adjusted to take into account the bootloader version currently installed on your device. Also check if the temporary system uses its own environment.