If you have the available resources, you could check out Microsoft office online. https://learn.microsoft.com/en-us/officeonlineserver/office-online-server

This can also be integrated with nextcloud afaik

Oh my sweet summer child…

Afaik there is an option in the autounattend tk run scripts at first logon. This could be used to run the ShutUp10 script and create a schuled task that keeps it enabled too