Filedes is not a tty

[Memarnejad]

Hi,
I'm testing the virtual tiny serial device (link) of book ldd3 in Ubuntu 20.04.6 (kernel version 5.15) . It gives the following error: FATAL: failed to add port: Filedes is not a tty
I had tested it in older version of ubuntu, i.e. 16.04, without any error with picocom.
Although, the virtual tiny tty (link) still works in ubuntu 20.04.6.
What is the reason of this error? and how to solve it?

picocom version: tested with both 3.1 and 3.2a

Thanks