Update:
Yes! Finally did it!
I was missing the MASQUERADE line in ufw
-A POSTROUTING -s 192.168.1.0/24 -o eth0 -j MASQUERADE
Ok not quite done yet as mitm proxy isn’t working yet but I got internet with that line above so I guess I just have to tweak the iptables rules a bit more to get mitmproxy working. I know where to focus my attention now.
EDIT: Got it. Just needed some more ufw/iptables tweaks.