What activity is there in Computer Go tournaments?
The  Computer Go Server1 is currently a very active test bed for bots. The Computer Go page at Sensei’s Library refers, under Competitions, to various competitions including the Computer Go Server, with its own page at Sensei’s Library, which gives the URL1. On that site, you will find daily updated tables of bots for 9×9, 13×13 and 19×19, These refer to the Bayes ELO ratings pages (on the same site) where for example the 19×19 page as I write (2020-04-19 22:17) shows 1064 programmes ranging in strength from DunceBot at 538 to KG30b11_406_2x2060 at 3387. The non-Bayes page shows the date+time of the most recent game by each bot, showing that a game was played some two hours ago.

The page http://www.computer-go.info/events/index.html, though was described at Sensei’s Library as showing “all competitions” in fact covers the dates 1920–20172.

I know no more than you of what has become of the UEC Cup. Surprisingly, none of the AlphaGo variants appear although one convincingly defeated a top professional, Lee Sedol, in 2016; more recent bots such as LeelaZero (released 2017-10-25) and KataGo (released 2019) appeared after the UEC Cup apparently stopped.

1  The current URL is http://www.yss-aya.com/cgos/ . Sensei’s also gave the URL http://cgos.boardspace.net/, but this appears not to work, which I have noted in Sensei’s.

2 I have updated Sensei’s accordingly.