Two routers in a network: OSPF on clients, ICMP redirects or something else?

Suppose a subnet with two routers: R1 is the main router and set as default gateway for all other nodes on that network. R2 is a secondary router

R1 and R2 are part of a larger network and know the Network topology via OSPF.

Now suppose an ordinary node of that network sends a packet which is sent to the default gateway (R1). R1 realizes that the proper router is R2. But since it’s the same subnet, R1 can’t just forward the packet to R2. Instead, it generates an ICMP redirect for the client.

However, it is widely recommended to disable ICMP redirect for security purposes.

So it may not be too great to rely on ICMP redirect to make routing work.

Alternatively I could install bird (OSPF) on each client node. But I am not sure if this is the right thing: Shouldn’t OSPF only belong on routers?

Are there other options I’m not seeing?