Surely yes, and in more generality, but can it be proved?

It seems that most, if not all, statements about quadratic forms representing primes fall back on algebraic number theory (i.e. splitting of primes in $\mathbb{Q}(\sqrt{7})$) for their proofs, and so are incompatible with the condition that $0 < y < x/10$.

Some related references which didn't lead to a proof: First of all there is this previous MO post, which suggests a negative answer.

There is also this paper of Iwaniec, which uses sieve methods but which also uses the multiplicative structure of solutions to the quadratic form.

There is also the interesting Theorem 5.36 of Iwaniec and Kowalski, which states that the arguments of prime elements of $\mathbb{Z}[i]$ are equidistributed in $(0, 2\pi)$. This is proved using the Hecke $L$-function $\sum_{\alpha \in \mathbb{Z}[i]} \big( \frac{\alpha}{|\alpha|} \big)^{ik} |\alpha|^{-s}$, for all $k$ divisible by 4. This generalizes further, but presumably not to real quadratic fields, where the infinite unit group would foul the construction up.

Finally, using a straight-up sieve (with only the additive structure of solutions to $x^2 - 7 y^2$) seems hopeless, as sieves tend to be bad at finding primes. There is the recent work of Friedlander-Iwaniec on $x^2 + y^4$ and Heath-Brown on $x^3 + 2y^3$, but these use algebraic number theory in $\mathbb{Q}(i)$ and $\mathbb{Q}(\sqrt{-3})$, and seem unlikely to generalize here.

I wonder if there is a promising approach out there which I have overlooked? Thank you!

obviouslytrue, for example see "On the relative sizes of A and B in p=A²+B², where p is a prime=1(mod 4)" math.carleton.ca/~williams/papers/pdf/237.pdf I guess Daniel Litt's comment is in similar spirit. $\endgroup$Algebraic number theory, Chap. XV, see Example 3 at the end of the chapter, in which equiditribution of Gaussian primes is (in some sense) generalized to the case of number fields with class number 1. $\endgroup$2more comments