Have you tried termination at ELB with TCP to backend, or just plain TCP passthrough all the way? Also as mentioned elsewhere, ALB or NLB might do what you wan

Have you tried termination at ELB with TCP to backend, or just plain TCP passthrough all the way? Also as mentioned elsewhere, ALB or NLB might do what you want, either working the same way as regular ELB or via the same workarounds.