Unlike the case with bases, AC is not needed to prove (even constructively) the existence of uncountable linearly independent subsets of $\mathbb{R}$ considered as a $\mathbb{Q}$-vector space, see e.g. https://mathoverflow.net/questions/23202/explicit-big-linearly-independent-sets
What if I'm not even interested in an explicit construction, but only in a merely existential proof (without AC), and I don't even want size continuum, but mere uncountability.
What's the simplest argument one can give?