Another option that may be worth trying is to do a backup of your Thread and Matter AddOns (UI->Settings->Backup-> +Create Backup, tick “partial” and choose these AddOns) on your Proxmox and then on your Zimaboard, remove the Matter/Thread Addons (restart the system) and then do a Restore onto your Zimaboard. You may have to adjust things like where the SkyConnect is located, but may just work, including the Android problem.
I was willing to give a try to the play services reset today, and I did not noticed your other answer.
I had a look to the partial backup options:
I have no entry for Thread. In my Proxmox VM installation, as well as on my Zimaboard.
Yeah “Thread” in your case is SiLabs Multiprotocol.
Also, ignore my suggestion about removing the AddONs, from Zimaboard. You probably want to keep those AddONs, but try to do a restore on them from what you backed-up from ProxMox.
I attempted to restore a partial backup that I uploaded to my Zigbee Home Automation (ZHA) installation.
Unfortunately, I encountered an issue
The primary problem is that the restored backup caused a mismatch between my ZHA channel (15) and thread channel (25):
border router “home-assistant” is configured with 15 (same than ZHA) when ha-thread-1b6f is configured with 25
I’m unsure if this situation is an improvement, as I’m still facing a final error “unable to locate device”.
I noticed that I did not have that “used for Android and iOS credentials” so I applied again the steps of exporting and importing the datasets TLV. I managed to get:
I also tried this:
Additionally, fixing the network channel issue is difficult because I’m using a Sonoff Zigbee dongle. Unlike the Sky Connect dongle, the Sonoff version lacks a system menu for channel adjustments.
This starts being a real nightmare, nothing I am trying is able to get my Matter and Thread work again 
Today I followed the instruction to clear the Google Play services on my phone.
Then the Matter integration was unavailable. I found a solution here to uninstall and reinstall the Google Home application.
Finally I again have that menu to add Matter device. I scan the code, it is looking for devices and fails: “This device needs a thread border router” issue
Here is the Thread setup
I also tried to make home-assistant the preferred network, but I think this is not the correct configuration
Hello !
Back again after a lot of experimentations.
I removed Silicon Labs Multiprotocol and I flashed the Sonoff Zigbee Dongle E back to Openthread RCP - Thread Only.
I then installed OpenThread Border router add-on, Thread, and Matter integrations.
Thread is looking good:
Here is also the OpenThread Border Router configuration:
And guess what … with the Android companion app, when I add one of my Thread device, I still get the error “your device needs a Thread border router” !
So I would say that my issue is not coming from the Silabs multiprotocol add-on, which is experimental. Now that I am running on something more standard, I still get this issue.
Does anyone has any idea what I can do to debug that issue ? My Thread network is now down for more than a month. I have not plenty of Thread devices, maybe 4, but I would like to test the new Matter 1.2 integration with my lock, and I still can’t 
Thanks !
Yeah, sorry I don’t really have any ideas as it takes many things coming together for Thread to work. My only real advice would be to factory reset all your devices, clear out the Android/Google-Play and see if you can then pair devices to your new setup.
Hello !
yes, no problem, I understand that not all cases can be solved 
I managed to fix my issue very recently.
I would like to explain in details how to solve it but I am even myself not so sure what fixed it and how so it will be hard to explain. But I will try.
I reverted my installation to basic OpenThread border router, no Silabs multiprotocol. Then I reset again Thread and Matter integrations. Here it was still not working, but in the companion app settings there is an entry that helped a lot: Companion app , go to Settings > Companion app > Troubleshooting, then select Sync Thread credentials.
Then thread worked, as well as matter.
But this is not what I wanted. I needed both zigbee and thread. So I restarted setting up silabs multiprotocol, thread, matter and zha. zha was still working, not thread. But again I synced through the companion app and it worked.
The result is quite suprising as I do not have a “named” thread network, but the one called “home assistant”. But it works. So I will not complain too much ^^
