It is now September 13, 2021. The TUG'21 (online) conference took place on August 5-8, and the community ad for the event was "live" only in the 2020 community ads for the TeX-LaTeX thread at tex.stackexchange.com. But it has just popped up on a new question. So the 2021 ads haven't been activated yet!
(However, the detail for both the 2020 and 2021 ads has been removed, so it's no longer possible to check anything.)
Please, please fix this!!!
To have this reappear so long after it's ceased being useful is a major embarrassment!
This same complaint has also been posted at https://meta.stackexchange.com/a/369797