The isomer transition of Th-229 has recently been excited for the first time by a VUV laser and subsequently the transition energy has been determined with a relative error of O(1e-6) (by now even O(1e-10)). Due to its enhanced sensitivity for scalars coupling to the nuclear sector compared to other optical clocks, measurements of the lineshape will soon start probing uncharted parameter space of ultra-light scalar dark matter. This is even before an optical clock based on this transition is realized. I will further discuss new possibilities to probe equivalence principle violating interactions mediated by these scalars over ranges larger than ~km as well as around ~nm.