@Aleks Thanks - that did the trick - backups can now be reinstalled 
but
after reinstall most apps just give me a “502 Bad Gateway nginx” page.
if i look into the nginx error log i see e.g. this:
/var/log/nginx/zyx.tld-error.log
coroutine 0:
[C]: in function 'lower'
/usr/share/ssowat/helpers.lua:1008: in function </usr/share/ssowat/helpers.lua:1001>, client: 91.204.46.37, server: xyz.tld, request: "POST /yunohost/sso/ HTTP/1.1", host: "xyz.tld", referrer: "https://xyz.tld/yunohost/sso/?r=aHR0cHM6Ly9pbS5hbGxtZW5kZW5ldHouZGUvaW5ib3g="
2022/08/11 17:00:49 [error] 224760#224760: *15119 [lua] helpers.lua:380: authenticate(): Connection failed for: marcó san 90, client: 187.248.44.146, server: xyz.tld, request: "POST /yunohost/sso/?r=aHR0cHM6Ly9taWNyb2Jsb2cuaW0uYWxsbWVuZGVuZXR6LmRlL0RpdmVydGlkYU5hbmN5 HTTP/2.0", host: "xyz.tld", referrer: "https://xyz.tld/yunohost/sso/?r=aHR0cHM6Ly9taWNyb2Jsb2cuaW0uYWxsbWVuZGVuZXR6LmRlL0RpdmVydGlkYU5hbmN5"
2022/08/11 17:01:34 [error] 224760#224760: *15119 [lua] helpers.lua:380: authenticate(): Connection failed for: marcó san 90, client: 187.248.44.146, server: xyz.tld, request: "POST /yunohost/sso/?r=aHR0cHM6Ly9taWNyb2Jsb2cuaW0uYWxsbWVuZGVuZXR6LmRlL0RpdmVydGlkYU5hbmN5 HTTP/2.0", host: "xyz.tld", referrer: "https://xyz.tld/yunohost/sso/?r=aHR0cHM6Ly9taWNyb2Jsb2cuaW0uYWxsbWVuZGVuZXR6LmRlL0RpdmVydGlkYU5hbmN5"
2022/08/11 17:01:43 [crit] 224762#224762: *15220 connect() to unix:/var/run/php/php7.3-fpm-wordpress.sock failed (2: No such file or directory) while connecting to upstream, client: 217.87.165.153, server: xyz.tld, request: "GET /apple-touch-icon.png HTTP/2.0", upstream: "fastcgi://unix:/var/run/php/php7.3-fpm-wordpress.sock:", host: "xyz.tld"
2022/08/11 17:01:43 [crit] 224762#224762: *15220 connect() to unix:/var/run/php/php7.3-fpm-wordpress.sock failed (2: No such file or directory) while connecting to upstream, client: 217.87.165.153, server: xyz.tld, request: "GET /favicon.ico HTTP/2.0", upstream: "fastcgi://unix:/var/run/php/php7.3-fpm-wordpress.sock:", host: "xyz.tld"
2022/08/11 17:01:55 [crit] 224762#224762: *15220 connect() to unix:/var/run/php/php7.3-fpm-wordpress.sock failed (2: No such file or directory) while connecting to upstream, client: 217.87.165.153, server: xyz.tld, request: "GET /apple-touch-icon.png HTTP/2.0", upstream: "fastcgi://unix:/var/run/php/php7.3-fpm-wordpress.sock:", host: "xyz.tld"
2022/08/11 17:01:55 [crit] 224762#224762: *15220 connect() to unix:/var/run/php/php7.3-fpm-wordpress.sock failed (2: No such file or directory) while connecting to upstream, client: 217.87.165.153, server: xyz.tld, request: "GET /favicon.ico HTTP/2.0", upstream: "fastcgi://unix:/var/run/php/php7.3-fpm-wordpress.sock:", host: "xyz.tld"
2022/08/11 17:02:04 [crit] 224760#224760: *15244 connect() to unix:/var/run/php/php7.3-fpm-wordpress.sock failed (2: No such file or directory) while connecting to upstream, client: 62.204.144.186, server: xyz.tld, request: "GET / HTTP/2.0", upstream: "fastcgi://unix:/var/run/php/php7.3-fpm-wordpress.sock:", host: "xyz.tld"
2022/08/11 17:02:04 [error] 224760#224760: *15244 open() "/var/www/wordpress/ynh_portal.js" failed (2: No such file or directory), client: 62.204.144.186, server: xyz.tld, request: "GET /ynh_portal.js HTTP/2.0", host: "xyz.tld", referrer: "https://xyz.tld/"
2022/08/11 17:02:04 [error] 224760#224760: *15244 open() "/var/www/wordpress/ynh_overlay.css" failed (2: No such file or directory), client: 62.204.144.186, server: xyz.tld, request: "GET /ynh_overlay.css HTTP/2.0", host: "xyz.tld", referrer: "https://xyz.tld/"
2022/08/11 17:02:04 [error] 224760#224760: *15244 open() "/var/www/wordpress/ynhtheme/custom_portal.js" failed (2: No such file or directory), client: 62.204.144.186, server: xyz.tld, request: "GET /ynhtheme/custom_portal.js HTTP/2.0", host: "xyz.tld", referrer: "https://xyz.tld/"
2022/08/11 17:02:04 [error] 224760#224760: *15244 open() "/var/www/wordpress/ynhtheme/custom_overlay.css" failed (2: No such file or directory), client: 62.204.144.186, server: xyz.tld, request: "GET /ynhtheme/custom_overlay.css HTTP/2.0", host: "xyz.tld", referrer: "https://xyz.tld/"
2022/08/11 17:02:04 [crit] 224760#224760: *15244 connect() to unix:/var/run/php/php7.3-fpm-wordpress.sock failed (2: No such file or directory) while connecting to upstream, client: 62.204.144.186, server: xyz.tld, request: "GET /favicon.ico HTTP/2.0", upstream: "fastcgi://unix:/var/run/php/php7.3-fpm-wordpress.sock:", host: "xyz.tld", referrer: "https://xyz.tld/"
2022/08/11 17:02:12 [error] 224760#224760: *15259 lua entry thread aborted: runtime error: /usr/share/ssowat/helpers.lua:1008: bad argument #1 to 'lower' (string expected, got nil)
stack traceback:
coroutine 0:
[C]: in function 'lower'
/usr/share/ssowat/helpers.lua:1008: in function </usr/share/ssowat/helpers.lua:1001>, client: 138.201.246.50, server: xyz.tld, request: "POST /yunohost/sso/ HTTP/1.1", host: "xyz.tld", referrer: "https://xyz.tld/yunohost/sso/?r=aHR0cHM6Ly9pbS5hbGxtZW5kZW5ldHouZGUvaW5ib3g="
2022/08/11 17:02:12 [error] 224760#224760: *15260 lua entry thread aborted: runtime error: /usr/share/ssowat/helpers.lua:1008: bad argument #1 to 'lower' (string expected, got nil)
stack traceback:
coroutine 0:
[C]: in function 'lower'
/usr/share/ssowat/helpers.lua:1008: in function </usr/share/ssowat/helpers.lua:1001>, client: 138.201.246.50, server: xyz.tld, request: "POST /yunohost/sso/ HTTP/1.1", host: "xyz.tld", referrer: "https://xyz.tld/yunohost/sso/?r=aHR0cHM6Ly9pbS5hbGxtZW5kZW5ldHouZGUvaW5ib3g="
2022/08/11 17:02:13 [error] 224760#224760: *15262 lua entry thread aborted: runtime error: /usr/share/ssowat/helpers.lua:1008: bad argument #1 to 'lower' (string expected, got nil)
stack traceback:
coroutine 0:
[C]: in function 'lower'
/usr/share/ssowat/helpers.lua:1008: in function </usr/share/ssowat/helpers.lua:1001>, client: 138.201.246.50, server: xyz.tld, request: "POST /yunohost/sso/ HTTP/1.1", host: "xyz.tld", referrer: "https://xyz.tld/yunohost/sso/?r=aHR0cHM6Ly9pbS5hbGxtZW5kZW5ldHouZGUvaW5ib3g="
2022/08/11 17:02:13 [error] 224760#224760: *15264 lua entry thread aborted: runtime error: /usr/share/ssowat/helpers.lua:1008: bad argument #1 to 'lower' (string expected, got nil)
stack traceback:
coroutine 0:
[C]: in function 'lower'
/usr/share/ssowat/helpers.lua:1008: in function </usr/share/ssowat/helpers.lua:1001>, client: 138.201.246.50, server: xyz.tld, request: "POST /yunohost/sso/ HTTP/1.1", host: "xyz.tld", referrer: "https://xyz.tld/yunohost/sso/?r=aHR0cHM6Ly9pbS5hbGxtZW5kZW5ldHouZGUvaW5ib3g="
2022/08/11 17:02:40 [error] 224760#224760: *15119 [lua] helpers.lua:380: authenticate(): Connection failed for: s19anmarco90@gmail.com, client: 187.248.44.146, server: xyz.tld, request: "POST /yunohost/sso/?r=aHR0cHM6Ly9taWNyb2Jsb2cuaW0uYWxsbWVuZGVuZXR6LmRlL0RpdmVydGlkYU5hbmN5 HTTP/2.0", host: "xyz.tld", referrer: "https://xyz.tld/yunohost/sso/?r=aHR0cHM6Ly9taWNyb2Jsb2cuaW0uYWxsbWVuZGVuZXR6LmRlL0RpdmVydGlkYU5hbmN5"
2022/08/11 17:03:29 [error] 224760#224760: *15119 [lua] helpers.lua:380: authenticate(): Connection failed for: marcó san 90, client: 187.248.44.146, server: xyz.tld, request: "POST /yunohost/sso/?r=aHR0cHM6Ly9taWNyb2Jsb2cuaW0uYWxsbWVuZGVuZXR6LmRlL0RpdmVydGlkYU5hbmN5 HTTP/2.0", host: "xyz.tld", referrer: "https://xyz.tld/yunohost/sso/?r=aHR0cHM6Ly9taWNyb2Jsb2cuaW0uYWxsbWVuZGVuZXR6LmRlL0RpdmVydGlkYU5hbmN5"
2022/08/11 17:03:30 [crit] 224760#224760: *15303 connect() to unix:/var/run/php/php7.3-fpm-wordpress.sock failed (2: No such file or directory) while connecting to upstream, client: 170.39.215.215, server: xyz.tld, request: "GET /.well-known/nodeinfo HTTP/2.0", upstream: "fastcgi://unix:/var/run/php/php7.3-fpm-wordpress.sock:", host: "xyz.tld"
2022/08/11 17:03:31 [crit] 224760#224760: *15307 connect() to unix:/var/run/php/php7.3-fpm-wordpress.sock failed (2: No such file or directory) while connecting to upstream, client: 170.39.215.215, server: xyz.tld, request: "GET /nodeinfo/1.0 HTTP/2.0", upstream: "fastcgi://unix:/var/run/php/php7.3-fpm-wordpress.sock:", host: "xyz.tld"
2022/08/11 17:03:36 [error] 224760#224760: *15310 lua entry thread aborted: runtime error: /usr/share/ssowat/helpers.lua:1008: bad argument #1 to 'lower' (string expected, got nil)
stack traceback:
coroutine 0:
[C]: in function 'lower'
/usr/share/ssowat/helpers.lua:1008: in function </usr/share/ssowat/helpers.lua:1001>, client: 185.26.156.246, server: xyz.tld, request: "POST /yunohost/sso/ HTTP/1.1", host: "xyz.tld", referrer: "https://xyz.tld/yunohost/sso/?r=aHR0cHM6Ly9pbS5hbGxtZW5kZW5ldHouZGUvaW5ib3g="
2022/08/11 17:04:15 [error] 224760#224760: *15119 [lua] helpers.lua:380: authenticate(): Connection failed for: marcosan90, client: 187.248.44.146, server: xyz.tld, request: "POST /yunohost/sso/?r=aHR0cHM6Ly9taWNyb2Jsb2cuaW0uYWxsbWVuZGVuZXR6LmRlL0RpdmVydGlkYU5hbmN5 HTTP/2.0", host: "xyz.tld", referrer: "https://xyz.tld/yunohost/sso/?r=aHR0cHM6Ly9taWNyb2Jsb2cuaW0uYWxsbWVuZGVuZXR6LmRlL0RpdmVydGlkYU5hbmN5"
2022/08/11 17:04:24 [error] 224760#224760: *15340 lua entry thread aborted: runtime error: /usr/share/ssowat/helpers.lua:1008: bad argument #1 to 'lower' (string expected, got nil)
stack traceback:
coroutine 0:
[C]: in function 'lower'
/usr/share/ssowat/helpers.lua:1008: in function </usr/share/ssowat/helpers.lua:1001>, client: 91.204.46.37, server: xyz.tld, request: "POST /yunohost/sso/ HTTP/1.1", host: "xyz.tld", referrer: "https://xyz.tld/yunohost/sso/?r=aHR0cHM6Ly9pbS5hbGxtZW5kZW5ldHouZGUvaW5ib3g="
invidious does not start
https://paste.yunohost.org/raw/zoquyegako
/var/log/nginx/error.log
find: '/usr/share/ssowat/portal/assets/themes/dark': No such file or directory