cal.com : Open source meeting scheduling tool. Send a link, let others book a slot. Calendly alternative.
YunoHost : YunoHost is a server operating system aiming to make self-hosting accessible to everyone.
Gitea : Gitea is a community managed fork of Gogs, lightweight code hosting solution written in Go and published under the MIT license.
Novu : The open-source notifications infrastructure. A fully-featured microservice to send SMS, E-mail, Slack and Push notifications. Embeddable notification...
GitPrep : GitPrep is Github clone. you can install portable github system into unix/linux. You can create users and repositories without limitation.