Unable to answer "What’s the topic of this information board?" – Information Board – https://osm.org/node/12195211605 via StreetComplete 59.0:

this board has no lock and members of the public can apparently add things to it. there are two lost dog posters, an add for a local pickleball tournament, and map of local trails.

Attached photo(s):
https://westnordost.de/p/241690.jpg