Matrix-Synapse version

Problem Description

I just started using my new FreedomBox and also installed and use the matrix server synapse.
I installed using plinth.
The version installed is 0.99.2. Newest version is about 1.9.
I need to upgrade, because this version does not yet support rooms version 4 and therefore users from this server can not join rooms of this version on other servers.

My question is: Is there any tweeking or such, or can I just add the debian repository of and apt-get update and upgrade?

Steps to Reproduce

  1. use some commandline on some server
    enter: curl -I https://yourservername:8448/_matrix/static/
    This will give you the version number of the installed server.

Thank you in advance!

Just give it one day for automatic updates to run. A new version of Matrix Synapse will be installed from backports.

Thank you for your help.