Which maths/physics conferences went online in 2020?

I am studying maths on my personal free time (and also am very interested in theoretical physics), at a graduate level, but I never got to attend to international conferences, as they require to go on-place, sometimes far in the world, and most of the time they span several days.

The pandemics has forced many seminars and conferences to go online (virtually all of those which have not been cancelled), and I strongly suspect that this is the same in maths and physics.

I can browse the web and already discover that many of these conferences are indeed online in 2020, but by asking HN I have these purpose:

1/ discover some interesting now-online conferences that I did not know of (remember, I am studying outside of any academic situation)

2/ ask whether there are good reasons to not keep these conferences (or part of them) online even after the outbreak. I, for one, would love that.

Thanks if you have any suggestions!