Do you have ethernet connected? It is quite possible video is what is cycling and it isn’t actually rebooting. The inability to go to recovery mode though is a concern…are you using the micro-B USB cable and the host does not show via “lsusb -d 0955:7c18”? I know you said you checked to make sure you were doing it right, but if the cable is type-A instead of type-B it won’t work.
Interrupting boot requires a serial console.
Note: If you have ethernet you can ssh in and correct any overwritten libglx.so file…this would be very likely to have happened if it is only video which is cycling and not an actual reboot. Should you be able to connect over ethernet check this:
sha1sum -c /etc/nv_tegra_release
If libglx.so shows as not correct, do this:
sudo rm /usr/lib/xorg/modules/extensions/libglx.so
sudo ln -sf /usr/lib/aarch64-linux-gnu/tegra/libglx.so /usr/lib/xorg/modules/extensions/libglx.so
# Then reboot.