ubuntu.social is one of the many independent Mastodon servers you can use to participate in the fediverse.
Mastodon server for official Ubuntu Members. This server is hosted and managed by Canonical.
To learn more about Ubuntu Membership, please visit: https://ubuntu.com/community/membership
If you like Xubuntu and Debian and cutting-edge rolling releases all at the same time, check out #Xebian. It's a Debian Sid derivative designed to feel and work like Xubuntu.