I could kick myself on the head… This is what I found in firewall.local:
# Force OpenVPN Client HTTP traffic through proxy server
iptables -t nat -A CUSTOMPREROUTING -i tun0 -p tcp --dport 80 -j DNAT --to-destination 192.168.0.1:801
Even with a nice comment stating my problem This is probably some leftover from years ago where I tried forcing all http traffic through the proxy… Completely forgot about it…
After removing that rule, it just works…
Many thanks for the pointer!