The Nextcloud documentation:
You can ask for help in our community support channels:
Please understand that all these channels essentially consist of users like you helping each other out. Consider helping others out where you can, to contribute back for the help you get. This is the only way to keep a community like Nextcloud healthy and sustainable!
If you run Nextcloud in a mission critical environment with large numbers of users and big amounts of data and need the certainty of support from the experts behind the Nextcloud technology, a Enterprise Subscription from Nextcloud is available with email and phone support.