New server breaks woltlab

I'm willing to pay if someone can help me with this.

I can't seem to find it, as this used to work:

I've migrated Woltlab to a new server, with the same PHP FPM + Nginx versions and configuration.

You would assume everything would keep on working, however I get a blank page everywhere.
No errors in the PHP error log.

I would expect an error to appear here if it would have been a memory limit issue?

/acp/ doesn't work neither to clear cache (also white).
Removing the contents of /wcf/cache doesn't solve it.
I've spent countless hours trying to make it work on the new server, but I can't find the issue.

Hereby my nginx rewrites in the Directadmin hosting panel:

if ($request_uri !~ (.*index\.php.*|/acp/js/.*)$ ) {

rewrite ^/Thread/(.*)/$ /index.php/Thread/$1/ break;
rewrite ^/Thread/(.*)$ /index.php/Thread/$1/ break;

rewrite ^/([a-zA-Z]*)/(.*)/$ /index.php/$1/$2/ break;

rewrite ^/acp/(.*) /acp/index.php/$1 break;
rewrite ^/([a-zA-Z]*)/$ /index.php/$1 break; 
}


location ~ [^/]\.php(/|$) {
                fastcgi_split_path_info ^(.+?\.php)(/.*)$;
                if (!-f $document_root$fastcgi_script_name) {
                        return 404;
                }

  fastcgi_read_timeout 300;
                fastcgi_pass unix:/usr/local/php56/sockets/domain.sock;
                fastcgi_index index.php;
                include fastcgi_params;
}

If I remove the entire last part:

location ~ [^/]\.php(/|$) {
  ...
}

Then the acp works fine, but
- the homepage offers to download itself

- If I visit a topic on url: https://www.domain.com/Thread/24970-topicTitle/

If I look in the php error log:

[error] 3917341#0: *454788 "/home/user/domains/domain.com/private_html/index.php/Thread/24970-topicTitle/index.php" is not found (20: Not a directory)

Ps: I tried the suggestions from other topics, but they don't work neither:

location / {
    index index.php;
    try_files $uri $uri/ @rewrite;
}

location @rewrite {
    rewrite ^/(forum/|cms/|wcf/|calendar/|filebase/|blog/|gallery/)?([^.]+)$ /$1index.php?$2 last;
}

Do you guys with a fresh look see what I'm doing wrong?

I need to get it running before I can update it.

I've tried updating it before, but it breaks a lot of custom code I wrote.

Aren't there any Woltlab skilled developer I can hire for this?

I remember again why I stopped updating Woltlab, I just tried it again:

I searched a lot in google, but no solution found so far.

- allow_url_fopen is enabled.
- no logs in the firewall that it would be blocked by it, same issue if I disable the firewall

Since on the new server nginx rewrites are no longer accepted (I get a 404 when updating in acp), I tried it on the old server, but there I get those ssl issues.

yum update ca-certificates returns:

Package ca-certificates-2020.2.41-65.1.el6_10.noarch already installed and latest version

So I'm fully stuck with no possibility to get it working.