Free entrance, played on OGS.
AGA, 7.5 komi for everything, schedule in UK timezone
9x9: 5 rounds, Swiss, 15m absolute 2020-08-12T18:30:00Z
13x13: 5 rounds, Swiss, 20m absolute 2020-08-14T18:30:00Z
19x19: 4 rounds, McMahon, 30m+10s/move up to 30m 2020-08-23T14:30:00Z
There’re a lot of other games: hex, shogi, chess, hive and so on and so on.
Edit: it already started but you can still register