Is it possible to do something similar as done for Teensy 3.2/3.5/3.6 described here:
with a teensy 4.0 ?

- Serial asynchronous interface in a half duplex mode
- RX and TX are physically connected through a resistor (2.4 kohms)
The bus is released in the following way: The TX line is reconfigured as an input with the use of an internal pull up
resistor. After the timeout has passed, the TX line returns into output state.