Well, I found a solution here OCC won't run with memcache/apcu - #7 by Reiner_Nippes - 🚧 Installation - Nextcloud community
I have edit the file /etc/php/7.3/mods-available/apcu.ini adding this line apc.enable_cli=1 and it works (using root)
I discover also this issue here Script et erreur PHP module local cache with another way to resolve the issue editing /etc/php/7.3/cli/php.ini in fact of /etc/php/7.3/mods-available/apcu.ini with the same line
Now the first permissions error is still here, I can’t use the user admin to use occ command…
/var/www/nextcloud$ ls -al
total 164
drwxr-xr-x 13 nextcloud nextcloud 4096 Sep 10 23:44 .
drwxr-xr-x+ 8 root root 4096 Oct 9 14:54 ..
drwxr-xr-x 43 nextcloud nextcloud 4096 Aug 26 15:27 3rdparty
drwxr-xr-x 61 nextcloud nextcloud 4096 Oct 9 14:45 apps
-rw-r--r-- 1 nextcloud nextcloud 19327 Aug 26 15:24 AUTHORS
drwxr-xr-x 2 nextcloud nextcloud 4096 Sep 10 23:44 config
-rw-r--r-- 1 nextcloud nextcloud 3924 Aug 26 15:24 console.php
-rw-r--r-- 1 nextcloud nextcloud 34520 Aug 26 15:24 COPYING
drwxr-xr-x 22 nextcloud nextcloud 4096 Aug 26 15:28 core
-rw-r--r-- 1 nextcloud nextcloud 5163 Aug 26 15:24 cron.php
-rw-r--r-- 1 nextcloud nextcloud 2836 Sep 10 23:44 .htaccess
-rw-r--r-- 1 nextcloud nextcloud 156 Aug 26 15:24 index.html
-rw-r--r-- 1 nextcloud nextcloud 3454 Aug 26 15:24 index.php
drwxr-xr-x 6 nextcloud nextcloud 4096 Aug 26 15:24 lib
-rw-r--r-- 1 nextcloud nextcloud 283 Aug 26 15:24 occ
drwxr-xr-x 2 nextcloud nextcloud 4096 Aug 26 15:24 ocm-provider
drwxr-xr-x 2 nextcloud nextcloud 4096 Aug 26 15:24 ocs
drwxr-xr-x 2 nextcloud nextcloud 4096 Aug 26 15:24 ocs-provider
-rw-r--r-- 1 nextcloud nextcloud 3139 Aug 26 15:24 public.php
-rw-r--r-- 1 nextcloud nextcloud 5340 Aug 26 15:24 remote.php
drwxr-xr-x 4 nextcloud nextcloud 4096 Aug 26 15:24 resources
-rw-r--r-- 1 nextcloud nextcloud 26 Aug 26 15:24 robots.txt
-rw-r--r-- 1 nextcloud nextcloud 2452 Aug 26 15:24 status.php
drwxr-xr-x 3 nextcloud nextcloud 4096 Aug 26 15:24 themes
drwxr-xr-x 2 nextcloud nextcloud 4096 Aug 26 15:25 updater
-rw-r--r-- 1 nextcloud nextcloud 101 Aug 26 15:24 .user.ini
-rw-r--r-- 1 nextcloud nextcloud 402 Aug 26 15:27 version.php