This is an Nlnet milestone.
Also check #2617 - Support link previews - karrot/karrot-frontend - Codeberg.org
Background
User story: Dave from Robin Foods has been using public activities feature and wants them to be more easily viewed (link preview) when sharing them in Telegram groups
Here’s an example of how it looks like
from Log: incoming feedback in raw format - #3 by bruno
From Nlnet MoU
Continue “breaking the silo”
Karrot supports public activities already, which can be discovered by a URL or on the group’s page (example Robin Foods). However, there is no possibility for people outside of a group or with no account on Karrot to sign-up for these activities. That is what this feature is about. We have identified from different communities and use cases that this would be very useful for them to interact with the wider public in their local community. This reduces their dependency on setting up events on big social media like Facebook.