GUI MQTT Client for esp-idf.
I used this component.
This component can communicate directly with the browser.
There is an example of using the component here. It's a great job.

I use this HTML & CSS.

Requires ESP32 with Flash Size 4M.
Models with a Flash Size 2M, such as the ESP32-C3, cannot be used.

git clone https://github.com/nopnop2002/esp-idf-mqtt-client
cd esp-idf-mqtt-client
git clone https://github.com/Molorius/esp32-websocket components/websocket
idf.py menuconfig
idf.py flash monitor

You can use the MDNS hostname instead of the IP address.

• esp-idf V4.3 or earlier
  You will need to manually change the mDNS strict mode according to this instruction.
• esp-idf V4.4 or later
  If you set CONFIG_MDNS_STRICT_MODE = y in sdkconfig.default, the firmware will be built with MDNS_STRICT_MODE = 1.

• Open browser.
• Enter the esp32 address in your browser's address bar.
• Press Connect button. You can use broker.emqx.io.
• Press Subscribe button.
• Enter the payload and press the Send button.