No MQTT devices, only MQTT entities

Where are the “devices” in MQTT integration?
In one version of Home Assistant (which was installed a long time ago (v2024.5.4)) there is a “devices” section, and in the other version (which was installed a month ago (v2024.5.5)) there are no devices.
What does it mean?
Where is the display mode switch?
I tried to remove the integration, restart Home Assistant and this integration offered to add it automatically. Added. Nothing changed.
I need the “devices” section!
Both versions are Home Assistant Supervised on Debain 12.

First of all, why do you need the ‘devices’, everything works as well with ‘entities’

Second, do your mqtt ‘entities’ create devices ? Easy to check with e.g. mqtt explorer. If they don’t, you will not see devices in the mqtt integration.

Absolutely right! Thank you!
If MQTT autodiscovery does not send a “device” section and none of the devices sent it, then that section is missing.
As soon as we send the “device” section in the configuration, this section appears

Example MQTT autodiscovery climate termostat:
topic: homeassistant/climate/thermostat4/config

  "device": {"identifiers": "tt4", "name": "BREmqtt4", "mf": "Breezart"},
  "name": "Вентиляция3",
  "temperature_command_topic": "breezart2/temp/set",
  "temperature_state_topic": "breezart2/temp/state",
  "mode_command_topic": "breezart2/mode/set",
  "mode_state_topic": "breezart2/mode/state",
  "modes": [ "off", "heat", "auto", "cool", "fan_only" ],
  "fan_modes": [ "high", "medium", "low" ],
  "temperature_unit": "C",
  "precision": 0.1,
  "temp_step": 0.5,
  "max_temp": 35,
  "min_temp": 5