Flash requires the micro-B USB port. If you simply need to change the root partition, then this can probably be achieved with a rescue SD card. However, upgrading to a new L4T version may not work because there are many hidden partitions on the eMMC which are also flashed when going to a new L4T version, and the hidden partitions may not be compatible with the new rootfs. It isn’t guaranteed, though it is possible it will work.
If you can RMA this is definitely the way to go. If traces are still in place where the connector broke off, then it is possible to put a new connector back on with a hot air rework station, but this requires significant skill (it’s surface mount with traces under the connector which is difficult to work on without harming the board).
If you are still interested, then you will want to test a rescue SD card, and a serial console would be nice (along with accepting that the module could become unreachable without flash if something goes wrong…the process is long and not guaranteed). See:
Are you interested in building an SD card for rescue?