Publishers offering "Community" spots

Community sponsorships are sponsored posts or pinned messages in a Discord, Slack, Telegram or forum community.

How to place an ad: Community sponsorships are booked directly with the community's operator, often by message or email.
When to use it: Discord, Slack, Telegram and forum communities are small, but members follow them closely, so a sponsored post gets more attention per member than a display ad.
Lead time: Usually a few days.