Hello, on ubuntu 16.04.4 my default iptables 1.6 policy for the INPUT & OUTPUT chain is DROP and i would like to add ACCEPT/ALLOW rule for local LAN IPs (so i can connect to lan and other LAN devices to me), i read some articles and they suggest example:

iptables -A INPUT 192.168.0.0/24 -j ACCEPT
iptables -A OUTPUT 192.168.0.0/24 -j ACCEPT

linux said:
ping: sendmsg: Operation not permitted

the reason was probably that the UFW firewall was not knowing about that rules.

So i want to ask how to allow it in UFW?

I tried: ufw allow out from 192.168.0.0/16 to 192.168.0.0/16

and it works to ping LAN IPs. Is it correct rule?

Next issue i see is if i stop ufw, then computer somehow bypass the VPN and connect directly. Even VPN is enabled (via OS built in connectivity manager, not using any vpn client).
When ufw is started, then per the ufw rules, only VPN connectivity is allowed and rest is blocked, so when i disable VPN, computer loose connectivity to the internet.

How can i prevent this IP leak during ufw being terminated/stopped/dead ?

Aim is not to allow bypassing VPN except LAN connections. Thank You

The same way you do in iptables (which you've been asking about for YEARS at this point). UFW is a FRONT END to iptables, and it even says so in the Ubuntu documentation. If you need to know how to allow something, you can use your YEARS of iptables experience and do so, or read the UFW documentation
https://help.ubuntu.com/community/UFW
You tell us...your network, is that what you want it to do?? If not, then no it isn't. If so....YES.
"Somehow"?? You're disabling all the rules, and (probably) have ipforwarding enabled. What do you think is going to happen?

If you don't want it to happen, then write a script or put some logic in the init scripts to shut networking off when firewall goes down.

Updating your thread title to get it to show back up isn't a good thing. Things aren't solved, because you've shown zero effort of your own, and haven't answered any questions you were asked.

If you don't do those things, your thread will REMAIN unsolved until you do.