Can't connect on DuckDNS

Thanks @Mutt, I tried the Nginx plug-in, but apparently it doesn’t play well with Synology as the Synology DNS has its own Nginx running.

But I did make the following changes as suggested throughout this thread:

Updated my configuration.yaml:

http:
  ssl_certificate: /ssl/fullchain.pem
  ssl_key: /ssl/privkey.pem
  base_url: https://customdomain.duckdns.org

I also made sure of @alekseyn’s reminder to forward port 443 to port 8123 of my HA (TCP protocol) on my router.

After these fixes, I managed to access my HA at https://customdomain.duckdns.org, but not at http://customdomain.duckdns.org (is this right?), and more crucially, not at its local IP.

I’m also getting this in my DuckDNS add-on log.

# INFO: Using main config file /data/workdir/config
ERROR: Lock file '/data/workdir/lock' present, aborting.

Unfortunately, it seems like an issue that others in that thread encountered as well.
Similar to this user, I can only access HA locally if I remove the above lines from configuration.yaml, but then I lose remote access through https instead.

Did you manage to find a solution to this?