Twisted conjugacy classes in general and special linear groups

We consider twisted conjugacy classes and the $R_\infty$-property for classical linear groups. In particular, it is stated that the general linear group $\mathrm{GL}_n(K)$ and the special linear group $\mathrm{SL}_n(K)$, for $n\ge3$, possess the $R_\infty$-property if either $K$ is an infinite integral domain with trivial automorphism group, or $K$ is an integral domain containing a subring of integers, whose automorphism group $\operatorname{Aut}(K)$ is finite. By an integral domain we mean a commutative ring with identity which has no zero divisors.