TerasIC DE10 NANO HDMI. Simplest example to start from, creating graphics.

Hard to tell what you're expecting, here, or what the problem may be. Terasic isn't generally known for having great code, but since it is mainly to verify components on your board are working it's not a huge obstacle.

The DE10 NANO simply uses the Analog Devices ADV7513 for HDMI TX. It's straightforward, and AD provides all the reference code you need to get started (see AN-1270). Start with the empty Golden reference Terasic provides, hook up the AD example code, and provide it all the right clock for your chosen resolution.