Update MQTT root on lora region change

[ford-jones]

Resolves #8139

🤝 Attestations

• I have tested that my proposed changes behave as described.
• I have tested that my proposed changes do not cause any obvious regressions on the following devices:
  • Heltec (Lora32) V3
  • RAK WisBlock 4631
  • Seeed Studio T-1000E tracker card
  • Seeed XIAO nRF2840 wio-sx1262

[ford-jones]

@ndoo suggested that we simultaneously clear the nodedb.
What do others think? 🤔

[ndoo]

I think one regression here is that if the user has a custom MQTT topic (perhaps some specific implementation on their own MQTT server), it would get reset by this change. May be inconveniencing that group of users for the convenience of this group of users.

What I assume would fix it is to generate the root topic with the old region and do a string comparison against the new generated root topic

[ford-jones]

@ndoo this should do it ^ 🙂
Still need to apply this logic to the menu handler then will pull this out of draft

[ndoo]

@ndoo this should do it ^ 🙂

Still need to apply this logic to the menu handler then will pull this out of draft

Thanks!

Hmm, I may be wrong here, but IIRC even the default generated topic will get saved to userPrefs so this block of code will functionally always enter the first if condition, hence necessitating doing an actual string comparison to determine if the topic is at default.

I.e. the userpref will only be empty if region is UNSET

[ndoo]

Sorry, I would love to test but am away from a device for 2-3 more days due to a work trip.

[ford-jones]

Ah, you're 100% correct ✔️
I've just gotten back home to test this and you're right about the preference being overwritten, I'll push something else up shortly 📡

[ndoo]

No worries, thanks for testing it.

…

On Tue, Sep 30, 2025 at 16:16 Ford Jones ***@***.***> wrote: *ford-jones* left a comment (meshtastic/firmware#8166) <#8166 (comment)> Ah, you're 100% correct ✔️ I've just gotten back home to test this and you're right about the preference being overwritten, I'll push something else up shortly 📡 — Reply to this email directly, view it on GitHub <#8166 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AACAFABF2A6W2ULJ3XTCWCL3VJC73AVCNFSM6AAAAACH3JEWFCVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTGNJQHA3TSNJQGE> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[Copilot]

Pull Request Overview

This PR updates the MQTT root topic to include the LoRa region name when the region is changed, ensuring proper MQTT topic subscription for different regions. The changes address issue #8139 by automatically updating MQTT configuration when LoRa region settings are modified.

• Adds logic to update MQTT root topic when LoRa region changes in admin configuration
• Updates menu handler to include MQTT root topic modification during region selection
• Updates protobuf submodule to latest version

Reviewed Changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 4 comments.

File	Description
src/modules/AdminModule.cpp	Adds region change detection and MQTT root topic update logic
src/graphics/draw/MenuHandler.cpp	Updates LoRa region picker to modify MQTT root topic and handle config changes properly
protobufs	Updates submodule to newer commit

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