Red Hat 7.3 Servers are indeed supported as noted in the NFA Linux System Requirements.
There are two workarounds:
1. Login to the server via a putty ssh session and install from there.
2. Or run the following command to install it via console mode:
./NFHarvesterSetup9.3.8.bin -i console
Either way it should allow you to install the NFA Harvester without error.