I have a Linux UHD Set-Top-Box VU+ Ultimo4k, which works with an ARM 4x1,5GHz Processor.
The Software running is the Vti-Community-Image ( see --== Vu+ Ultimo 4K und Image ==-- - Vu+ Support Forum ).
Meanwhile I have learned, this Image is a busybox-Linux.
Do you see the possibility, that your great NextCloud-Software runs with Docker on Ultimo4k-Hardware?
Okay, it must be an easy way like the NextCloudPi-Image, because this solution runs at my home 
Thanks,
habeas