> at least Trump knew what they were

There is zero evidence that Trump has any clue UIB exists.

The exact quote from him was that the head of the Homeland Security's science and technology division told him they were going to test it:

"And then I said, supposing you brought the light inside the body, which you can do either through the skin or some other way, and I think you said you're going to test that, too."

We have two scenarios here:

1) Trump knew about UBI, a fringe medical practice used primarily in Russia decades ago

2) Trump heard them talking just moments before about how UV light disinfects outdoor surfaces and kills the virus, and that using chemical disinfectants also killed the virus, and then proceeded to talk about how you could inject disinfectant or put UV light inside the body.

Occam's Razor would point us towards the latter. It's just a lot less convoluted to believe he was talking about the same topic the entire prior discussion had been around than to believe he's talking about an obscure and unproven medical practice decades removed from use.

But... that's not even a description of this technique. To be clear, this technique does not in any way involve putting a UV source inside the body. It's more like dialysis, in that it happens externally. The only similarity to what Trump was wittering on about is that it involves UV. It's very unlikely to have been what gave him the idea.

> To be clear, this technique does not in any way involve putting a UV source inside the body.

There are people who do it both ways. As another commenter pointed you, you can buy devices that do the same thing that work inside the body:

https://vielight.com/

That's also not internal; it's on the surface. See https://en.wikipedia.org/wiki/Low-level_laser_therapy

Not a medical expert, but Encyclopedia Britannica seems to say that the nasal cavity counts as an internal space:

https://www.britannica.com/science/nasal-cavity