Multiple serial receivers support

In manual it’s possible, i’ve set RC_OPTIONS bit 10
But i’m still getting error: PreArm: Multiple SERIAL ports configured for RC in

Which Flight Controller do you have?

Holybro Pixhawk 6C
20 chars…

So you have one receiver connected to the standard RCIN port and the 2nd connected to a serial port and only that serial port protocol is set to 23?

i want to have 2 RCIN ports to be set to 23, is that possible?

No. That’s not how it works. The primary Rx is on the IOMCU (RCIN port) and the 2nd one is on a serial port. You can only have one serial port selected for protocol 23. And why would you want to do that anyway?