The Infomaniak Status page has been updated with the explanation for the service disruption:
https://infomaniakstatus.com/en/n9qB8RXPjQ/
The incident resulted from a malfunction during the execution of an automated maintenance script dedicated to DNS zone management. This script inadvertently modified the name servers of our primary domain and its sub-domains, interrupting name resolution for our entire infrastructure.
Source: r/Infomaniak · by /u/mailavion