solved: ERROR: no matching function for call to 'LiquidCrystal_I2C::begin()'

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From LiquidCrystal_I2C/LiquidCrystal_I2C.h at 1.1.3 · johnrickman/LiquidCrystal_I2C · GitHub

void begin(uint8_t cols, uint8_t rows, uint8_t charsize = LCD_5x8DOTS );

As I expected, that library's begin() requires parameters. In fact none of its examples even use begin(). As I said, there are multiple libraries of this name so likely you are looking at examples written for a different library.