Discourse ActivityPub integration doesn't work

[strk]

Despite following the gfoss_it Discourse category from Mastodon, users are not receiving messages from it.

Here's the tab showing the set of ActivityPub follows: ​https://discourse.osgeo.org/ap/category/33/followers

Here's a thread on mastodon about not receiving them (in italian): ​https://mastodon.uno/@strk/112925842579517041

[strk]

It actually works with @general@…, see ​https://mapstodon.space/@general@discourse.osgeo.org

While it doesn't work with @gfoss-it@…, see ​https://mapstodon.space/@gfoss-it@discourse.osgeo.org

I'm following both actors from a mapstodon.space account

[strk]

Comparing the settings of the two categories I don't see many differences.

1. Use of a dash in the name (gfoss-it)
2. Nesting level (local-chapters/gfoss-it)