Short Term Treasury Bond ETFs like SGOV – RISKS?

Alright, I've tried my best to read through all this, and my head just won't wrap around it.

What are the risks of owning a short term treasury bond ETF like SGOV? Like is the only thing that will keep me from at least getting my principal out at anytime a collapse of the US government? If the market absolutely tanks, is their risk that I'll lose my principal?

I know I could just do a HYSA, but I want to keep a chunk of my money in my TDA account.

THANKS!