Also, did you change the variables in the Lemmy UI environment?
(Edit to specify, in the docker-compose.yml file the variables are now different)
The lemmy-ui environment variables have changed, and should now look like:
environment:
- LEMMY_UI_LEMMY_INTERNAL_HOST=lemmy:8536
- LEMMY_UI_LEMMY_EXTERNAL_HOST={{ domain }}
- LEMMY_UI_HTTPS=true
There are also other instructions that you need to follow. Are you following the release note instructions?