i had the idea that two gateways could work in the same network without issues… in my inexperience i tried it with three hosts on an hyperv virtual network and it worked.
my stupid idea it’s like this:
main router 192.168.1.1
opnsense LAN connected to a switch on router LAN1 192.168.1.254
opnsense WAN 192.168.1.2 (still on the switch on the router LAN2)
pc1 static IP address 192.168.1.3 with main router as gateway and this works
PC2 DHCP assigned by opnsense in a pool from 192.168.1.50 to 192.168.1.100 with opnsense 192.168.1.254 as gateway
why i do this? To have a “temporary” setup where i slowly move all the static ip addresses to opnsense and in this way everything can have a valid configuration