Successful Synapse installation isnt assigned an URL

My YunoHost server

Hardware: Old laptop or computer /
YunoHost version:
I have access to my server : Through SSH & through the webadmin & direct access via keyboard / screen
Are you in a special context or did you perform some particular tweaking on your YunoHost instance ? : no

Description of my issue

After a successful manual installation of Yunohost on Debian and a Nextcloud app install, I thought I might get into the federation with a Synapse server.
Installation seems to succeed but the app isn’t assigned an URL for some reason.
TTRSS installs fine and is assigned an URL as expected, haven’t tried any other installations.
Also, I cannot Redirect domain root to Synapse (python error).
Nor can I change the access URL of this application (greyed out)

Install Logs:

Note that Synapse is only a server so it doesn’t actually have an interface … If youexpect to use Matrix from your server, then you shall install Riot which is the client part. (Or maybe some already existing Riot instance allow you to connect to a different Synapse server idk)

Gosh I feel incredibly dense right now. :face_with_hand_over_mouth:
Installed the client with the oneliner under the install section :