[Harri (OP)]

Are there any particular standout discoveries and advancements made so far this year in the world of science?

[Halc]

Wiki has a page on it: https://en.wikipedia.org/wiki/2021_in_science

Topping the list is a first ever Earth spinning faster than 24 hours in a day, leaving them pondering the possibility of a negative leap-second rather than just waiting for some other year to absorb it. That might not happen as the slowing of Earth's spin has been decreasing for some time and it might continue to speed up for a while despite the negative torque on it. I think it has to do with the moment of Earth changing due to global warming.

The next most interesting thing I found in January was a system of 6 exoplanets orbiting TOI-178 in which the outer five planets are locked in a chain of Laplace resonances. It's close by, suggesting that the resonance is more common than previously thought. We have some moons thus locked, but no pairs of planets.

[evan_au]

One story that attracted my attention was detecting half of the matter in the universe, which only previously been hypothesized.
It's really hard to detect the extremely rarified hydrogen in intergalactic space, but Fast Radio Bursts give some hints about its density. 

[Bored chemist]

Are there any particular standout discoveries and advancements made so far this year in the world of science?

Almost certainly, but it may take a year or two before we recognise them.