The noncocompact \operatorname{SL}$3$ arithmetic-subgroup conjecture

Let $\Gamma$ be a noncocompact arithmetic subgroup of either $\operatorname{SL}(3,\mathbb{R})$ or $\operatorname{SL}(3,\mathbb{C})$. A faithful action on $\mathbb{R}$ means an action with trivial kernel. The noncocompact $\operatorname{SL}(3)$ conjecture. Noncocompact arithmetic subgroups of $\operatorname{SL}(3,\mathbb{R})$ and $\operatorname{SL}(3,\mathbb{C})$ have no faithful action on $\mathbb{R}$. This is identified as a special case that would establish the main conjecture under the additional assumption of noncocompactness. The source gives no resolution.