Integration of IoT devices with Tasmota and MQTT in a single Android app, local WiFi

I have insisted that the company does not use IoT devices that connect to the 'manufacturer's cloud'. I don't want to raise the discussion here why this and not the "convenient cloud". I need your hint on how to integrate several elements (e.g. with Tasmota where MQTT is among other things) so that this can then be handled in a single android application (local WiFi connection) - without having to log in to each device separately.

I can set up something on Linux internally - or at least that's how I imagine it, maybe wrongly.

[Edit]
The title came up with AI so.... sorry.

xury wrote:

You didn't write what specific Android app you want to use.

"The simplest. The app must be.

xury wrote:

But you can also use MqttDashboard. And you build this dashboard for yourself already on the phone.

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This seems like a poor solution for the needs I'm going for. The app is needed so that this automation can be used/read remotely (e.g. open the gate by driving up in a car). Building the same thing in several apps is a poor idea - any updates / changes would have to be made to multiple users. The app is only supposed to be an 'end device' to operate the whole thing (fairly simple operation) so I imagine there is 'some sort of control panel' where I can do the configuration and to it an app for the phone.

Added after 43 [minutes]: .

If I understand Nodered correctly, this is exactly the kind of "control panel" where I will be able to create events, dependencies, etc.

What then for an App that will serve as a frontend to Noderered ?

gulson wrote:

why not home assistant?

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I don't know if you don't.

Although I have had automation for many years I have no experience in solutions with Domoticz , Home Assistant, Node-RED or anything like that.

I need something that will do for the frontend itself on Android and on the iPhone i.e. without being able to make changes to the configuration of this automation.
The second condition - no cloud solutions, just operation from the local network. I can buy hardware and put something locally on Linux.
On executive devices I prefer Tasmota but I don't insist.