2 interfaces 2 defaults gateways : bad idea

I have on my haos 2 interfaces. One for access to public things, one for access private IOT network that is severly firewalled.
The problem is haos REQUIRES 2 gateways… one for enp0s5f0 (the interface with internet access), one for enp0s5f1 (the one for IOT network). I wanted to add interface to my ipcam networks, but I will not do that.
Is it possible to network GUI to let NOT configure defaut gateway for one interface?