Can't get UARTs to work with RTS/CTS

I’m really wanting UART5 with RTSCTS enabled.

If I use the BB-UART5-00A0.dtbo, I am able to get my serial port working.
During boot process a link file called /dev/ttyO5 is created.

If I use the BB-UART5-RTSCTS-00A0.dtbo, no link file is created
during boot and my attempts to use the ttyS5 serial port fail.

I have disabled the BB-HDMI.
I don’t see any boot messages about pin clash.

I’m really stuck.

Any ideas?
There must be some secret sauce I haven’t found yet.

My serial test is using minicom. But, since it does not create the
link file ttyO5 during boot (with RTSCTS overlay), I think things go bad
at a lower level before I come on the scene.

I have tried other UARTs and have had no success with any of them
when using the RTSCTS overlays.