I forgot to announce (and so that it is documented) that Alan had asked me if in Discourse the timer of the topics could be configured as countdown to close the topic automatically.
I told him that not natively, but then I installed the theme component (it’s not a plugin) “Live Topic Timer” that does that (Live Topic Timer - theme - Discourse Meta)
So, if someone sets a timer on a topic (wrench, “Set topic timer”), the format will be automatically a countdown from now on.