…or will the SD card take one UART channel?
Greetings,
Kajetan
The SD card interface on the Teensy 4.1 is connected via the SDIO (Secure Digital Input Output) interface rather than UART. Therefore, using an SD card won’t consume one of the UART channels.
With that said, the Teensy 4.1 has eight Serial objects available in software, which you can use to emulate additional UART channels. These software serial ports can be utilized in parallel with the hardware UARTs and the SD card interface.
So…yes 
Wow. I’ts a very, very good news. 
I want connect eight diferent ESP32 modules by UART, and saving transfered codes on SD.
Thanks a lot,
Kind regards,
Kajetan