Last time piwik was updated (2017) the update failed in a non recoverable way. IIRC this was due to the db server being outdated. Add a result we haven't collected any stats for e.g. wikipedia.se.
We should update/migrate the database server, renewable piwik and add an SSL certificate for it.
Both the piwik server and the db server likely host other services which we need to ensure survive the transition.