I got redsocks up and running in less than 10 mins, it's really no rocket science....
if using nftables
create 99-redsocks.nft in /etc/nftables.d, and paste the following into it
chain REDSOCKS {
# hook to the output/prerouting
type nat hook prerouting priority dstnat; policy accept;
# skip for local ip ranges
ip daddr 0.0.0.0/8 return
ip daddr 10.0.0.0/8 return
ip daddr 100.64.0.0/10 return
ip daddr 127.0.0.0/8 return
ip daddr 169.254.0.0/16 return
ip daddr 172.16.0.0/12 return
ip daddr 192.168.0.0/16 return
ip daddr 198.18.0.0/15 return
ip daddr 224.0.0.0/4 return
ip daddr 240.0.0.0/4 return
# everything else tcp = redirect to redsocks
ip protocol tcp redirect to 12345
}
restart the network service, or reboot the router afterwards.
if using iptables
install iptables iptables-mod-nat-extra in addition to redsocks, and apply the iptables rules found on internet, only slightly modified to match OpenWRT's LAN interface.
iptables -t nat -N REDSOCKS
iptables -t nat -A REDSOCKS -d 0.0.0.0/8 -j RETURN
iptables -t nat -A REDSOCKS -d 10.0.0.0/8 -j RETURN
iptables -t nat -A REDSOCKS -d 100.64.0.0/10 -j RETURN
iptables -t nat -A REDSOCKS -d 127.0.0.0/8 -j RETURN
iptables -t nat -A REDSOCKS -d 169.254.0.0/16 -j RETURN
iptables -t nat -A REDSOCKS -d 172.16.0.0/12 -j RETURN
iptables -t nat -A REDSOCKS -d 192.168.0.0/16 -j RETURN
iptables -t nat -A REDSOCKS -d 198.18.0.0/15 -j RETURN
iptables -t nat -A REDSOCKS -d 224.0.0.0/4 -j RETURN
iptables -t nat -A REDSOCKS -d 240.0.0.0/4 -j RETURN
iptables -t nat -A REDSOCKS -p tcp -j REDIRECT --to-ports 12345
iptables -t nat -A PREROUTING -i br-lan -p tcp -j REDSOCKS
iptables -A INPUT -i br-lan -p tcp --dport 12345 -j ACCEPT
Don't forget to customize your /etc/redsocks.conf file too.
not very pretty, but I suck at firewall rules, I still use shorewall (not on OpenWRT) 
1751008062.934829 info redsocks.c:1243 redsocks_accept_client(...) [192.168.1.157:53498->208.79.209.138:443]: accepted
1751008063.208377 debug redsocks.c:341 redsocks_start_relay(...) [192.168.1.157:53498->208.79.209.138:443]: data relaying started
1751008064.087770 info redsocks.c:671 redsocks_drop_client(...) [192.168.1.157:53498->208.79.209.138:443]: connection closed
1751008064.768139 info redsocks.c:1243 redsocks_accept_client(...) [192.168.1.157:53499->2.21.240.94:443]: accepted
1751008065.426704 debug redsocks.c:341 redsocks_start_relay(...) [192.168.1.157:53499->2.21.240.94:443]: data relaying started