netboot.xyz is a way to PXE boot various operating system installers or utilities. It’s really handy to be able to install Linux distributions in a test environment. netboot.xyz is based on iPXE.
At home, I run a Unifi USG which serves as my gateway to the internet and TrueNAS Core run my TFTP server (amongst other services).
Via the Unifi Controller, go to Settings > Networks > LAN Network > Edit. Then go to “ADVANCED DHCP OPTIONS” and check “Enable network boot” and enter the IP address of the TFTP server and specify “netboot.xyz.kpxe” (which needs to be downloaded to the location specified in the TrueNAS Core TFTP settings.)