This is the way.

If you have a dynamic WAN IP (like I do), you can make use of DDNS-updater services such as this.

Also, afaik, Immich does not have chunked uploads yet (not sure if it has been updated to include that) so you might have to check your DNS' policies regarding traffic (e.g. Cloudflare proxy only allows up to 100Mb traffic and can't be used to serve media from what I read).