Anyone find a solution to this? I have the same problem: Brand new installation of HA on Docker, on an Unbuntu 20.04 box
First time on launching from the client, I get the HA welcome page - but create account button is greyed out. On refreshing, or launching a second time, I get an ERR_CONNECTION_REFUSED error.
Connections between the Unbuntu box and the client (a Win 11 PC) are fine - can ping both ways, and a Plex server on the same box is working fine.