If you connect an antenna to an active cable TV service lead... even one that has been limited to internet access only, you risk causing harmful interference to aircraft, fire, police and military frequencies.
If you are unable to get satisfactory reception using an indoor antenna, you will want to review the
FCC OTARD rules which protect your right to receive OTA signals.
You should be able to find a workable solution without needing to 'fight' with your landlord.