Hi,
Thanks for the report.
I believe the issue is OMV applies a default webserver configuration file, that limits the system to OMV usage only. You’d need to either tweak our default webserver config file (https://github.com/Fourdee/DietPi/blob/master/dietpi/conf/apache2_jessie.conf) to include support for OMV (unsure how at the moment), or, manually add server configs for NextCloud.
We cant control OMV, or really support it along side dietpi-software/dietpi-config, its just not compatible. Ideally, i’d recommend using solely DietPi and the tools available, to replace OMV entirely.
As we cant truly support OMV along side DietPi, I may consider removing it from the DietPi-Software catalog to prevent similar issues reported by our users.