Whoever gets that link can browse it in a web browser.
I've used this to share albums of photos with gatherings of folks; it works very well. It does assume you have your Immich installation publicly available, however. (Not open to the public, but on a publicly accessible web server)
it’s not a fair comparison with Google because Google has a much bigger target on their back. There are millions of users of Google, so the value of hacking Google is very high. The value of hacking a random Immich instance is extremely low.
Flip a switch and then what, are you getting a isolated public URL to share? Or you have your infrastructure exposed to the internet and the shared URL is pointing to your actual server where the data is hosted?
Setup immich VM or docker container with a cloudflare tunnel
Front access with Cloudflare Access (ZeroTrust) for free.
Set "can only be accessed by users with email = xyz@myuser”
Done.
Now assuming this is the same user email as the one you shared photos with, there is a base level of security keeping the riffraff away.
Home IP is never exposed either, because it's proxied through the cf tunnel.
I think the previous commenter misunderstood your question, this is the answer (you can also put it behind something like cloudflared tunnels).
Immich is a service like any other running on your server, if you want it exposed to the internet you need to do it yourself (get a domain, expose the service to the internet via your home ip or a tunnel like cloudflared, and link that to your domain).
After that, Immich allows you to share public folders (anyone with the link can see the album, no auth), or private folders (people have to auth with your immich server, you either create an account for them since you're the admin, or set up oauth with automatic account creation).
I keep that running on a VPS, but with with proper firewalling you could probably run it on the same machine.