JOSHR3ll

Thanks again for your help, you were right, the solution does work, but only if the process is followed very strictly. I can see why others may have failed or stopped midway.
In my case, if I didn’t do:
downgrade to 4.0.41
factory reset at that exact stage
only use the correct command to bypass the wizard
then upgrade
it would break things badly (I had HTTP redirection to /dumaweb, SSL issues, Windows Update failing, etc.).
Regarding your question about the 24h disconnect:
Before this full process, I had hard disconnections every ~24 hours with no automatic reconnection at all ; I had to manually reboot the router each time.
Now, after applying the full method, everything is stable. It has been 48 hours without any disconnection or need to reboot, so for now it looks like the issue may be completely resolved.
What I’ve also identified is that the issue seems to be triggered specifically after performing a factory reset on firmware 4.0.540 or 4.0.645. After that, PPPoE auto-reconnection stops working correctly. Using the 4.0.41 reset + upgrade method seems to avoid that state entirely.
I’ll continue monitoring to confirm over a longer period, but this is already very promising.
Also interesting to hear you're running 4.0.645 successfully, that gives me confidence to maybe test it later, once I’m sure everything is stable on my side.

Thank you; I now know that the solution does, in fact, work for others, albeit with some bypassing involved. I have suggested the solution to others in the past, but I don't think anyone has actually persevered until the end.
I have promptly used the latest firmware versions, as they are released, with the solution. I am currently using firmware version 4.0.645. The only slight problem I have encountered, which may be unrelated to the solution, is that the '--' fails to load occasionally. This problem has only started to occur more recently, and it resolves itself after some time without any intervention.
One last question: do the 24-hour disconnects still occur but automatically reconnect afterwards, or do they no longer occur altogether?
 

That's great to hear, thanks for the update! I would suggest staying on your current version as I cannot guarantee the kind of stability for your issue that you're looking for on that version at the moment.

From my testing, my solution only works if the factory reset is on firmware version 4.0.41. Firmware version 4.0.41 was the last firmware with PPPoE working. Any factory reset after that firmware will break it again.
The solution was to automatically reconnect when a disconnect occurs. I'm unsure whether it will prevent your disconnections from happening altogether.

@JOSHR3ll try this command as one command please instead:
await duma.RPCHandler.PostRPC({rapp:"com.netdumasoftware.config",method:"set_web_setup_done",params:[true]});
await duma.RPCHandler.PostRPC({rapp:"com.netdumasoftware.config",method:"set_setup_done",params:[true]});

perfect thanks

It's tied to the cookies in your browser so if you have the browser set to clear cache/cookies every time you close the browser or tab for example then it will show you the tour each time. Ensure cache/cookies persist for the interface and once completed shouldn't show again

Added