To add to the list (the order is arbitrary):
5. Advances in the multi-messenger observations, where apart of photons and gravitational waves, astronomers can detects also neutrinos with specialized neutrino detectors, e.g.: IceCube [a], though there are many more of those [b].
6. Advances in very-long-baseline interferometry [c] using a globe-sized array of radio-telescopes, like Event Horizon Telescope [d]
[a] https://en.wikipedia.org/wiki/IceCube_Neutrino_Observatory
[b] https://en.wikipedia.org/wiki/Neutrino_detector or here https://en.wikipedia.org/wiki/List_of_neutrino_experiments
[c] https://en.wikipedia.org/wiki/Very-long-baseline_interferome...