I am unable to delete a default route permanently on my Raspberry Pi 3 B+.

RPi 3 B+, Kali 2020, onboard wifi, usb wifi

ip route:
Code:
default via 192.168.1.1 dev wlan0 online
default via 192.168.1.1 dev wlan1 proto dhcp metric 600
192.168.1.0/24 dev wlan1 proto kernel scope link src 192.168.1.139 metric 600
192.168.4.0/24 dev wlan0 proto kernel scope link src 192.168.4.1
wlan1 onboard wifi connects to local wifi router, wlan0 wifi dongle serves lan traffic that is local only - mainly for ssh/VNC to RPi.

After boot, I am unable to access internet with browser directly from RPi until I delete the first route from table:
ip route del default
(Only removes first default)

Success, the first line is gone from ip route and I can connect to internet - until reboot. Once I reboot, tables are restored again :'(

I have already deleted /etc/iptables.ipv4.nat after I deleted the default route, then ran iptables-save. When I execute iptables-save to view all saved routes (without >), there are NO entries in the output. /etc/network/interfaces has iptables-restore < /etc/iptables.ipv4.nat at the end.

I am running networking, NetworkManager, dnsmasq, udhcpd. The default route on wlan0 seems to be loading from somewhere during boot but I can't find it. Not in dnsmasq.conf, .d/*.conf or udhcpd.conf. Any help is very much appreciated.

Note: NetworkManager seems to load stuff from setting defaults and interfaces but I can't find any references to wlan0 in the configs using grep.