3/ Second, itβs important to note that there is no single OSM community, there are many. Some are focused on specific geographies (country, region, etc), some are based on shared interests (mapping cycle infrastructure for example) or shared languages.
4/ Different #OpenStreetMap communities (or people within those communities) use different tools and platforms to communicate.
Mailing lists are common https://lists.openstreetmap.org/listinfo, but some prefer IRC, Facebook, Telegram, forums, some are active here in the fediverse, etc. It really varies. The world is a diverse place