I know about some results providing some upper bounds for the cardinality of sets like $\mathcal{N}_{\mathcal{B}}(x):=\{n\leq x : p\mid n \Rightarrow p\in \mathcal{B}\}$, where $\mathcal{B}$ is the union of distinct reduce residues classes modulo $q$ (one of the most useful is due to Chang and Greg Martin: The smallest invariant factor of the multiplicative group, Int. J. Number Theory (2020), 16, 182, 1377–1405.)
However, I was trying to get an upper bound for the set of positive integers $n\leq x$ for which $n$ has exactly one prime factor of the form $4k+3$.
I tried to use Chang and Martin result, but I was not able to do it.
Any suggestion? Thanks in advance.