Foreman is provisioning machines via PXE properly, and logs show that the TFTP server is servicing requests, but when navigating to

• Infrastructure > Smart Proxies
• Click Smart Proxy FQDN
• Click Services tab

...and in the section for TFTP, the TFTP Server section shows false.

I mentioned this to Ohad Levy on IRC, and he said:

thats actually a bug in displaying the data, as the tftp proxy has the ability to override its name from configuration, so if its not set, then its shows as false.

Here's a screenshot showing the bug in action:

Finally, for reference, I used the following line to perform my foreman installation

foreman-installer --scenario katello --foreman-proxy-dhcp=true --foreman-proxy-dns=true --foreman-proxy-tftp=true

... at least the last time I ran it. I had initially specified more options, but I reset it over a dozen times.