I managed to solve it myself:
frontend sniproxy
bind *:443
mode tcp
tcp-request inspect-delay 5s
tcp-request content accept if { req_ssl_hello_type 1 }
use_backend alias if { req.ssl_sni -m beg alias }
default_backend fqdn
backend fqdn
mode tcp
server host 127.0.0.1:5665
backend alias
mode tcp
server host 127.0.0.1:8443 send-proxy-v2
my issue was that i useed send-proxy instead of send-proxy-v2