If you want true random you need the dice and ditch the LLM; like another commenter pointed out LLMs are pseudorandom with varying degrees of randomness, that can be set by the one who created the tool in question. It's never going to be as random as basic, unaltered dice can be. A bit of human curated randomness has a lot more warmth and meaning than the coldness of a fancy autocomplete warped in it's basic function. Which a person who thinks and talks to their partner could put some thoughtful surprises in the mix easily enough. Meh, to each their own.

LLMs (and most computer applications) don't operate with true random number generators, mostly pseudorandom generators of varying degrees of strength of randomness.

Physical dice are more likely to be actually random than most computer stuff. Unless they're loaded or otherwise biased.