OK,
Ran both from server root as administrator and directly from the site path, got the following responses:
“An unhandled exception has been thrown:”
OCP\HintException: [0]: Memcache \OC\Memcache\APCu not available for local cache (Is the matching PHP module installed and enabled?)
Thought Memcache was installed when I ran sudo apt install memcached libmemcached-tools
Also configured memcached.conf for IPv6, & UDP.
MORE ABOUT INSTALLATION:
I installed to a headless server from a remote terminal, manually.
The server is my own hardware running several sites, my root domain and sub-domains. Nextcloud is installed to sub-domain.domain.com in the nextcloud directory.
I am trying to resolve the issues from setting/overview:
"The database is missing some indexes. Due to the fact that adding indexes on big tables could take some time they were not added automatically. By running “occ db:add-missing-indices” those missing indexes could be added manually while the instance keeps running. Once the indexes are added queries to those tables are usually much faster.
Missing index "fs_id_storage_size" in table "oc_filecache".
Missing index "fs_storage_path_prefix" in table "oc_filecache".
Missing index "properties_pathonly_index" in table "oc_properties".
Missing index "job_lastcheck_reserved" in table "oc_jobs".
Missing index "direct_edit_timestamp" in table "oc_direct_edit".```"