@Mathieu I do use NGINX Proxy Manager and i have no issues accessing XO-CE via the new v6 default or the old v5 with working links.

As @probain has stated there have been quite a few updates pushed to fix most issues. My issues were related to the script i used to install XO-CE. The script creator had to update the script to the recent changes made.

Make sure you are on the latest commit and/or update your script and try again.