Riemann Hypothesis
Establish whether all nontrivial zeros of the Riemann zeta function ζ(s) lie on the critical line Re(s) = 1/2.
References
Indeed, Riemann assumed in 1859 that all nontrivial zeroes are placed on the line $Re(s)=\frac{1}{2}$. This is the famous Riemann's hypothesis. This problem has attracted considerable interest from many mathematicians, although after 163 years, it remains unsolved.
                — The Generalized Riemann Zeta heat flow
                
                (2402.10154 - Castillo et al., 15 Feb 2024) in Section 1.1 (Setting)