Hello,
sorry, but i posted a part of my problem also in Thread: Teensy 4.0 First Beta Test. But there are so many posts that i fear my post will go under and it is not in the right thread.

Maybe someone has a solution.

After installing Arduino IDE 1.8.9 and Teensyduino 1.47 beta 6 i connected Teensy 4 with Adafruit 1,8" Color TFT LCD display with MicroSD Card Breakout ( https://www.adafruit.com/product/358 ).
I am using following pins:
MISO - pin12
SCK - pin13
MOSI - pin11
TFT_CS - pin10
Card_CS - pin4
D/C - pin9
Reset - pin8
VCC - 3,3V
Gnd - Gnd
But i had no success in using library ST7735_t3 (in ...Arduino\hardware\teensy\avr\libraries)

in example spiffbitmap : (with SD Card) : Initializing SD Card - failure -> Screen is white ....
(without SD Card): Initializing SD Card - failure -> Screen is blach with message: Unable to access SD Card

Then i tried graphicstest: Text is ok, most graphics also, but in the end there were objects on the screen that were not right.
rotationtest: black screen

I cross checked 2 Displays with my Teensy 3.6 and they are ok.

I need both (TFT LCD display and Micro SD Card) on this board working with Teensy 4 (without changing much of the above mentioned wiring)
(so example spiffbitmap is the most important one what should run with Teensy 4)

Is the problem of Initialization failure of the SD Card because that pin 4 isn't a fast CS pin on Teensy 4 anymore? (Teensy 3.6 has 2 fast CS pins)

Thank you

best regards
Erik