The Corona Cup was a series of three online amateur tournaments held on KGS in 2020 and 2021, during the namesake coronavirus (Covid-19) pandemic and associated lockdown.
The first two editions (?) were held in 2020 and the third in 2021.
It was organised, at least in part, by Czech professional Lukáš Podpěra. It was supported  by the Czech Go Association and the EGF, and sponsored by the Jena International Go School (JIGS) and the Nordic Go Dojo.
The entry fee was €10 or 250 Czech koruna, with a discounted fee of €6 / 150 koruna for pensioners and under-15s. There was a first prize of €300, and further prizes of €300 JIGS vouchers for the top three players in each of the U12, U16 and U20 youth categories.
The tournament was a six round McMahon, with a time control of 1 hr + 3 x 30s.
The Corona Cup series is of historical importance as (one of?) the first major amateur tournaments held online after home AI was made available in 2017, having to create an anti-cheating policy without much precedent available. The heated and long running controversy over the proper extent of anti-botting measures deserves its own article, and as such should not be elaborated on here.
To quote the policy of the third edition:
"It’s not allowed to use any joseki dictionaries, AI or outside help. (...) arbiters will check played games (...) using state-of-the-art anti-cheating tools. If the arbiters find it clear that a player has cheated, all of the player‘s games will be forfeited and the player disqualified immediately.
(...) All dan players are obliged to use webcameras during their games (...) . The video should be taken from the side, so that the computer’s screen, player’s mouse hand, and the player’s face are all visible. For other players this is optional, but highly recommended." 
 whatever that means