A 3.3 V board and a 5 V part

/*
  Logic Level Converter - loopback check                TK97 / /p/tk97

  Two channels, both ways, with one jumper and no other part. Socket
  at the top, both rows start at GND at the left.

  A 3.3 V board (ESP32, ESP32-S3, Pico) goes on the OUT side:

    GND    -> GND
    5V     -> 5V (VBUS on a Pico). The TK97 makes its own 3.3 V.
    3V3    -> nothing. It is the TK97's output, never your 3V3.
    L1     -> OUT_PIN
    L2     -> BACK_PIN
    H1, H2    joined to each other with one jumper.

  An Uno goes on the IN side: GND and 5V the same, H1 -> OUT_PIN,
  H2 -> BACK_PIN, and one jumper from L1 to L2 in the socket.

  OUT_PIN goes out through channel 1, over the jumper and back
  through channel 2 to BACK_PIN.

  Arduino IDE
    Tools > Board                 your board, e.g. ESP32S3 Dev Module
    Tools > Port                  the one that appears when you plug in
    Tools > USB CDC On Boot       Enabled   (ESP32-S3 only)
    No library needed.
    Serial Monitor                115200
*/

// The pin wired to L1 (H1 on an Uno).
// Uno: 2. ESP32: 25. ESP32-S3: 4. Pico: 14.
const int OUT_PIN = 4;
// The pin wired to L2 (H2 on an Uno).
// Uno: 3. ESP32: 26. ESP32-S3: 5. Pico: 15.
const int BACK_PIN = 5;

// Time for a level to cross twice before it is read. Microseconds
// would do; a millisecond keeps it obvious.
const int SETTLE_MS = 1;

int sendAndRead(int level) {
  digitalWrite(OUT_PIN, level);
  delay(SETTLE_MS);
  return digitalRead(BACK_PIN);
}

void setup() {
  Serial.begin(115200);
  pinMode(OUT_PIN, OUTPUT);
  // No pull-up here: the TK97's own 10 kOhm holds the line.
  pinMode(BACK_PIN, INPUT);
}

void loop() {
  int high = sendAndRead(HIGH);
  int low = sendAndRead(LOW);

  if (high == HIGH && low == LOW) {
    Serial.println("HIGH came back HIGH, LOW came back LOW: ok");
  } else if (high == HIGH && low == HIGH) {
    Serial.println("always HIGH: check the jumper, and BACK_PIN");
  } else if (high == LOW && low == LOW) {
    Serial.println("always LOW: check 5V and GND, then OUT_PIN");
  } else {
    Serial.println("backwards: check every wire against the list");
  }
  delay(1000);
}

"""
  Logic Level Converter - loopback check, MicroPython   TK97 / /p/tk97

  Two channels, both ways, with one jumper and no other part. Socket
  at the top, both rows start at GND at the left. The board goes on
  the OUT side:

    GND    -> GND
    5V     -> 5V (VBUS on a Pico). The TK97 makes its own 3.3 V.
    3V3    -> nothing. It is the TK97's output, never your 3V3.
    L1     -> OUT_PIN: GPIO 25 on an ESP32, GPIO 4 on an S3, GP14
    L2     -> BACK_PIN: GPIO 26 on an ESP32, GPIO 5 on an S3, GP15
    H1, H2    joined to each other with one jumper.

  Thonny
    Run > Configure interpreter   MicroPython (ESP32) or
                                  MicroPython (Raspberry Pi Pico)
"""

import time
from machine import Pin

# GPIO numbers. ESP32: 25 and 26. ESP32-S3: 4 and 5. Pico: 14 and 15.
OUT_PIN = 4
BACK_PIN = 5

out = Pin(OUT_PIN, Pin.OUT, value=0)
# No pull-up here: the TK97's own 10 kOhm holds the line.
back = Pin(BACK_PIN, Pin.IN)


def send_and_read(level):
    out.value(level)
    time.sleep_ms(1)
    return back.value()


while True:
    high = send_and_read(1)
    low = send_and_read(0)
    if high == 1 and low == 0:
        print("HIGH came back HIGH, LOW came back LOW: ok")
    elif high == 1 and low == 1:
        print("always HIGH: check the jumper, and BACK_PIN")
    elif high == 0 and low == 0:
        print("always LOW: check 5V and GND, then OUT_PIN")
    else:
        print("backwards: check every wire against the list")
    time.sleep(1)