Arduino Settings

I am using actually (05/2021) the Arduino IDE v1.8.13/v1.8.15/v1.8.16 with the ESP32 Package v1.0.5/v1.0.6/v2.0.0.
See here Installation instructions using Arduino IDE Boards Manager for how to add ESP32 Support to your Arduino IDE.

U8g2 Display Library

You need to add the U8g2 Library from Oli Kraus to your Arduino System.
Use the Arduino IDE Library Manager (Sketch > Include Library > Manage Libraries) and search for U8g2.
Important: As we use an Display with a Pixel width of 256 we need to uncomment // Enable U8G2_16BIT in u8g2.h.
See 16-Bit-Mode for more details.
➡️ It looks like the 16-Bit-Mode is automatically enabled if you use an ESP Device. No need to enable it manually.

Choose your Board

Starting with the USB-Version of 2021-05-27 you only need to choose the correct Board in the Arduino IDE.
The Arduino IDE and the Sketch should detect the chosen Board and enable the needed settings automatically.
Functionality tested with Arduino IDE 1.8.13/1.8.15, ESP32 Package 1.0.5/1.0.6, ESP8266 Package 3.0.0/3.0.1.
!! Important !!
Uncomment only Your Board

Arduino IDE Settings for an TTGO-T8 v1.7.1 with 16MB Flash

Choose "ESP32 Dev Module" as Board within the Arduino IDE
Uncomment #define USE_TTGOT8

Arduino IDE Settings for an Wemos Lolin32

Choose "WEMOS LOLIN32" as Board within the Arduino IDE
Uncomment #define USE_LOLIN32W

Arduino IDE Settings for an ESP8266-NodeMCU v3

Choose "NodeMCU 1.0 (ESP-12E Module)" as Board within the Arduino IDE
Uncomment #define USE_NODEMCU

SD Card information

Format your SD Card with FAT16 (FAT) or FAT32.
SD Cards can be used in SPI or SD-Bus Mode with the ESP32 with Arduino & ESP's.
The TTGO-T8 supports SPI and the 1-Bit SD-Bus Mode.
One weird thing is that you need to run the SD_MMC.begin("/sdcard", true) command twice to get it working.
The first command reports an error back, the second one is working fine.
This issue is reported on some websites and be hopefully fixed in newer Releases of the ESP32 Package.
The 4-Bit SD-Bus Mode, which is not supported by the TTGO-T8's SD Slot, doesn't show this weird issue.