YunoHost is an operating system aiming to simplify as much as possible the administration of a server. You can visit yunohost.org or forum.yunohost.org for more information or help.
6. In the basic information tab, you'll find a "Client ID" and a "Signing Secret" - you'll need them to run the package installation
7. Go to "Features" then "OAuth & Permissions"
8. Add a new redirect URL. Use https://mydomain.fr/path/auth/slack.callback (with mydomain.fr/path being the domain on which you will install outline package)