Fresh install failing - gnutls_handshake() failed: Error in the pull function

My main question here is, COULD this issue be the MTU of the network adapter that Discourse is using (the docker interface)?

Because if the issue COULD be with the MTU i can make further attempts to change it, if the issue CANT be the MTU then i can pressure my hosting provider further.

They will not go any further until i have confirmed that the issue is NOT the MTU as they are adamant there will be connection issues using an MTU of 1500.

If you cant assist with changing the MTU of the network adapter that discourse is using then who would be able to assist? Docker support?