Hi!
Sorry for the delay to answer you, I gave up for a while about updating my router but now I`m trying to do it again.
No, there is nothing special in my set up. In 3.105 if I reset to default config and I just set up the PPPoE it works. I do the same procedure in 3.203 and it does not connect.
I just created a topic with the messages the router shows while trying to connect, maybe you could take a look at that:
GL-MV1000 - PPPoE not working after update to 3.203 - Routers / software - GL.iNet (gl-inet.com)