After spending considerable time fighting the exact issues described in this thread — PCA9557/GT911 touch initialization failures, LVGL driver conflicts, WiFi killing the display, and incorrect board settings — I have documented a complete working solution and published it on GitHub.
The short version of what nobody tells you:
The flash size in Arduino IDE must be set to 4MB. The board ships configured for 16MB which is incorrect for the actual hardware. This single setting causes cascading failures that look like touch problems, LVGL problems, and WiFi problems but are actually all rooted in the same misconfiguration.
The “Bus already started in Master Mode” warning in the serial monitor is non-halting and can be ignored. Touch will initialize correctly with the proper reset sequence once the board settings are correct.
Complete working configuration, all resolved issues, locked board settings, full source code for a dual-screen glassmorphism system monitor pulling live data at 33 FPS, and the Flask daemon that feeds it are all documented and available here:
Hope this saves someone the hours I lost getting here.
73 de W2LPC