Slow Sync with client

Nextcloud version (eg, 12.0.2): 24.0.3
Operating system and version (eg, Ubuntu 17.04): Debian 11
Apache or nginx version (eg, Apache 2.4.25): Nginx 1.23.0
PHP version (eg, 7.1): 8.1

Database: mariadb 10.6.8
Desktop sync clients: Windows and MacOS

The issue you are facing:
When syncing a folder (no matter if normal sync or as virtual files) the download becomes really slow (maximum download is 1mb/s).

nginx.conf:

user www-data;
worker_processes auto;
pid /var/run/nginx.pid;
events {
worker_connections 2048;
multi_accept on; use epoll;
}
http {
server_names_hash_bucket_size 64;

access_log /var/log/nginx/access.log;
error_log /var/log/nginx/error.log warn;
# set_real_ip_from 127.0.0.1;
real_ip_header X-Forwarded-For;
real_ip_recursive on;
include /etc/nginx/mime.types;
default_type application/octet-stream;
sendfile on;
send_timeout 3600;
tcp_nopush on;
tcp_nodelay on;
open_file_cache max=500 inactive=10m;
open_file_cache_errors on;
keepalive_timeout 65;
reset_timedout_connection on;
server_tokens off;
#resolver 127.0.0.53 valid=30s;
#resolver_timeout 5s;
include /etc/nginx/conf.d/*.conf;
}

nginx virtual host:

server {
listen 443      ssl http2;
listen [::]:443 ssl http2;
server_name cloud.xxxxxxx;
ssl_certificate /etc/letsencrypt/rsa-certs/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/rsa-certs/privkey.pem;
ssl_certificate /etc/letsencrypt/ecc-certs/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/ecc-certs/privkey.pem;
ssl_trusted_certificate /etc/letsencrypt/ecc-certs/chain.pem;
ssl_dhparam /etc/ssl/certs/dhparam.pem;
ssl_session_timeout 1d;
ssl_session_cache shared:SSL:50m;
ssl_session_tickets off;
ssl_protocols TLSv1.3 TLSv1.2;
ssl_ciphers 'TLS-CHACHA20-POLY1305-SHA256:TLS-AES-256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA512:DHE-RSA-AES256-GCM-SHA512:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES256-GCM-SHA384';
ssl_ecdh_curve X448:secp521r1:secp384r1;
ssl_prefer_server_ciphers on;
ssl_stapling on;
ssl_stapling_verify on;
client_max_body_size 200G;
client_body_timeout 3600s;
fastcgi_buffers 64 4K;
gzip on;
gzip_vary on;
gzip_comp_level 4;
gzip_min_length 256;
gzip_proxied expired no-cache no-store private no_last_modified no_etag auth;
gzip_types application/atom+xml application/javascript application/json application/ld+json application/manifest+json application/rss+xml application/vnd.geo+json application/vnd.ms-fontobject application/wasm application/x-font-ttf application/x-web-app-manifest+json application/xhtml+xml application/xml font/opentype image/bmp image/svg+xml image/x-icon text/cache-manifest text/css text/plain text/vcard text/vnd.rim.location.xloc text/vtt text/x-component text/x-cross-domain-policy;
add_header Strict-Transport-Security            "max-age=15768000; includeSubDomains; preload;" always;
add_header Permissions-Policy                   "interest-cohort=()";
add_header Referrer-Policy                      "no-referrer"   always;
add_header X-Content-Type-Options               "nosniff"       always;
add_header X-Download-Options                   "noopen"        always;
add_header X-Frame-Options                      "SAMEORIGIN"    always;
add_header X-Permitted-Cross-Domain-Policies    "none"          always;
add_header X-Robots-Tag                         "none"          always;
add_header X-XSS-Protection                     "1; mode=block" always;
fastcgi_hide_header X-Powered-By;
root /var/www/nextcloud;
index index.php index.html /index.php$request_uri;
location = / {
if ( $http_user_agent ~ ^DavClnt ) {
return 302 /remote.php/webdav/$is_args$args;
}
}
location = /robots.txt {
allow all;
log_not_found off;
access_log off;
}
location ^~ /apps/rainloop/app/data {
deny all;
}

location /installclient/clientinstall_macos.sh {
alias /var/www/installclient/clientinstall_macos.sh;
}
location /installclient/Installation_Mac-Client.pdf {
alias /var/www/installclient/Installation_Mac-Client.pdf;
}
#location /installclient/info.php {
#alias /var/www/installclient/info.php;
#}

location ^~ /.well-known {
location = /.well-known/carddav { return 301 /remote.php/dav/; }
location = /.well-known/caldav  { return 301 /remote.php/dav/; }
location /.well-known/acme-challenge { try_files $uri $uri/ =404; }
location /.well-known/pki-validation { try_files $uri $uri/ =404; }
return 301 /index.php$request_uri;
}
location ~ ^/(?:build|tests|config|lib|3rdparty|templates|data)(?:$|/)  { return 404; }
location ~ ^/(?:\.|autotest|occ|issue|indie|db_|console)                { return 404; }
location ~ \.php(?:$|/) {
rewrite ^/(?!index|remote|public|cron|core\/ajax\/update|status|ocs\/v[12]|updater\/.+|oc[ms]-provider\/.+|.+\/richdocumentscode\/proxy) /index.php$request_uri;
fastcgi_split_path_info ^(.+?\.php)(/.*)$;
set $path_info $fastcgi_path_info;
try_files $fastcgi_script_name =404;
include fastcgi_params;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
fastcgi_param PATH_INFO $path_info;
fastcgi_param HTTPS on;
fastcgi_param modHeadersAvailable true;
fastcgi_param front_controller_active true;
fastcgi_pass php-handler;
fastcgi_intercept_errors on;
fastcgi_request_buffering off;
fastcgi_read_timeout 3600;
fastcgi_send_timeout 3600;
fastcgi_connect_timeout 3600;
fastcgi_max_temp_file_size 0;
}
location ~ \.(?:css|js|svg|gif|png|jpg|ico|wasm|tflite|map)$ {
try_files $uri /index.php$request_uri;
add_header Cache-Control "public, max-age=15778463, $asset_immutable";
expires 6M;
access_log off;
location ~ \.wasm$ {
default_type application/wasm;
}
}
location ~ \.woff2?$ {
try_files $uri /index.php$request_uri;
expires 7d;
access_log off;
}
location /remote {
return 301 /remote.php$request_uri;
}
location / {
try_files $uri $uri/ /index.php$request_uri;
}
location /push/ {
proxy_pass http://localhost:7867/;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "Upgrade";
proxy_set_header Host $host;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}
}

nextcloud config.php

<?php
$CONFIG = array (
  'instanceid' => 'oc4bggribkxe',
  'passwordsalt' => 'xxxxx',
  'secret' => 'xxxxx',
  'trusted_domains' =>
  array (
    0 => 'cloud.xxxxxx',
    1 => '10.0.0.2',
  ),
  'datadirectory' => '/mnt/ncdata/data',
  'dbtype' => 'mysql',
  'version' => '24.0.3.2',
  'overwrite.cli.url' => 'https://xxxxxx',
  'dbname' => 'nextclouddb',
  'dbhost' => 'localhost',
  'dbport' => '',
  'dbtableprefix' => 'oc_',
  'mysql.utf8mb4' => true,
  'dbuser' => 'nextclouddbuser',
  'dbpassword' => 'xxxxxx',
  'installed' => true,
  'activity_expire_days' => 30,
  'allow_local_remote_servers' => true,
  'auth.bruteforce.protection.enabled' => true,
  'blacklisted_files' =>
  array (
    0 => '.htaccess',
    1 => 'Thumbs.db',
    2 => 'thumbs.db',
  ),
  'cron_log' => true,
  'default_phone_region' => 'DE',
  'default_language' => 'de',
  'default_locale' => 'de_DE',
  'defaultapp' => 'files,dashboard',
  'enable_previews' => true,
  'enabledPreviewProviders' =>
  array (
    0 => 'OC\\Preview\\PNG',
    1 => 'OC\\Preview\\JPEG',
    2 => 'OC\\Preview\\GIF',
    3 => 'OC\\Preview\\BMP',
    4 => 'OC\\Preview\\XBitmap',
    5 => 'OC\\Preview\\Movie',
    6 => 'OC\\Preview\\PDF',
    7 => 'OC\\Preview\\MP3',
    8 => 'OC\\Preview\\TXT',
    9 => 'OC\\Preview\\MarkDown',
  ),
  'filesystem_check_changes' => 0,
  'filelocking.enabled' => 'true',
  'htaccess.RewriteBase' => '/',
  'integrity.check.disabled' => false,
  'knowledgebaseenabled' => false,
  'logfile' => '/var/log/nextcloud/nextcloud.log',
  'loglevel' => '2',
  'logtimezone' => 'Europe/Berlin',
  'log_rotate_size' => '104857600',
  'maintenance' => false,
  'memcache.local' => '\\OC\\Memcache\\APCu',
  'memcache.locking' => '\\OC\\Memcache\\Redis',
  'overwriteprotocol' => 'https',
  'preview_max_x' => 1024,
  'preview_max_y' => 768,
  'preview_max_scale_factor' => 1,
  'profile.enabled' => false,
  'redis' =>
  array (
    'host' => '/var/run/redis/redis-server.sock',
    'port' => 0,
    'timeout' => 0.5,
    'dbindex' => 1,
  ),
  'quota_include_external_storage' => false,
  'sharing.enable_share_accept' => false,
  'skeletondirectory' => '',
  'theme' => '',
  'trashbin_retention_obligation' => 'auto, 7',
  'updater.release.channel' => 'stable',
  'mail_smtpmode' => 'sendmail',
  'mail_sendmailmode' => 'smtp',
  'mail_from_address' => 'cloud',
  'mail_domain' => 'xxxxxx',
  'trusted_proxies' =>
  array (
    0 => '127.0.0.1',
    1 => '::1',
  ),
  'remember_login_cookie_lifetime' => '',
  'versions_retention_obligation' => 'auto, 365',
  'simpleSignUpLink.shown' => false,
  'upgrade.disable-web' => true,
  'log.condition' =>
  array (
    'apps' =>
    array (
      0 => 'admin_audit',
    ),
  ),
  'twofactor_enforced' => 'false',
  'twofactor_enforced_groups' =>
  array (
  ),
  'twofactor_enforced_excluded_groups' =>
  array (
    0 => '123_ADMIN',
  ),
  'app_install_overwrite' =>
  array (
    0 => 'documentserver_community',
  ),
);