Flickering Mini PiTFT 1.14" on Uno R4 Wifi

[leonpierre]

• Arduino board: Arduino Uno R4 Wifi
• Arduino IDE version: 2.1.1
• List the steps to reproduce:

`#define TFT_CS 10
#define TFT_RST -1 // -1 for unused
#define TFT_DC 8

const uint16_t Display_Color_Black = 0x0000;
const uint16_t Display_Color_Blue = 0x001F;
const uint16_t Display_Color_Red = 0xF800;
const uint16_t Display_Color_Green = 0x07E0;
const uint16_t Display_Color_Cyan = 0x07FF;
const uint16_t Display_Color_Magenta = 0xF81F;
const uint16_t Display_Color_Yellow = 0xFFE0;
const uint16_t Display_Color_White = 0xFFFF;

uint16_t Display_Text_Color = Display_Color_White;
uint16_t Display_Backround_Color = Display_Color_Black;

Adafruit_ST7789 tft = Adafruit_ST7789(TFT_CS, TFT_DC, TFT_RST); // Hardware SPI init

void setup()
{
tft.init(135, 240);
tft.setFont();
tft.setRotation(135); // 135 or 45
tft.fillScreen(Display_Backround_Color);
tft.setTextColor(Display_Text_Color);
tft.setTextSize(2);

tft.print("TEST");
}`

Should output TEST and that's it, but flickers and only shows the text if I press the Reset button on the R4 Wifi. The same code is working fine on an e.g. Arduino Nano.

Do I have to use another SPI mode (although tried everything) or adjust the SPI speed or is the new R4 not yet supported?
Link to issue on Arduino forum: https://forum.arduino.cc/t/flickering-mini-pitft-1-14-with-st7789-library/1145766