Three volts only

The rule is printed on the board

Turn a board over to its connector face and find the boxed warning. It says the board is for 3.3 volt microcontrollers such as an ESP32-S3 or a Raspberry Pi Pico, and that a 5 volt board such as an Uno R3 needs a logic level converter to avoid damaging the display.

That is not a disclaimer. It is the operating condition, and it is the single most expensive thing to get wrong with these boards. There is no regulator and no level shifter on them: what you put on the 3V3 hole and on the signal holes is what the panel gets.

What actually happens

A pin on a 5 V board, driven high, puts 5 V on a wire. The input it arrives at was built for a chip running from 3.3 V, and inputs like it usually have a protection diode from the pin up to that supply. A few tenths of a volt above the supply, that diode starts conducting, and current flows from your Uno, through the display's input, into the display's own supply rail.

Sometimes that survives. Sometimes it browns out the panel, which is the flicker the silkscreen warns about, and sometimes it kills the input. The failure that makes people give up is the slow one: a display that works for an afternoon and is dead the following week, with no single moment you can point at.

The two safe arrangements

A 3.3 V board. An ESP32, an ESP32-S3, a Pico, an STM32, an nRF52. Wire the holes straight across and there is nothing to think about. The Lonely Binary library runs on the first two of those and no other chip, so a library user is in this case already.

A 5 V board with a converter. Put a level converter on every line heading towards the display that reaches the controller: SCL, MOSI, DC, RST and CS. Run the 3V3 hole from a 3.3 volt supply, not through the converter, because a converter shifts signals and does not make power.

BL is the sixth signal and a different case. It goes to the gate of the backlight transistor and not to the controller, so it is not one of the five that reach the panel's inputs. Driving it from a 3.3 V level is the same simple rule as the rest, and the board's own 10 kΩ resistor holds the lamp off while you do not.

Five lines is more than a two-channel board has, so this is the case for an eight-channel shifter rather than a small MOSFET board. The converter handbook covers which is which.

And a thing worth checking either way

The lamp switches on all at once. If your host browns out or resets at the moment the display lights up, that is not a logic level problem. It is a supply that has no headroom, and the cure is a rail that can carry it.