Hi,as title I would know if is possible to use the hdd attached to the router as a storage for nextcloud,and if is possible how. Using the merlin firmware obviously.
Thanks
HQT has a tutorial for the predecessor of Nextcloud, owncloud.
I'm not sure that the router can handle this well, but you can always try.
Just adapt the commands for Nextcloud: https://www.hqt.ro/owncloud-through-lighttpd-entware-ng/