So this issue was completely on my end.
I configured the IPSec VPN on the other end (Oracle OCI) as Static routing rather than Policy and that only allows one child SA.
There's not issue on Opnsense's end.
I configured the IPSec VPN on the other end (Oracle OCI) as Static routing rather than Policy and that only allows one child SA.
There's not issue on Opnsense's end.