Tangential to the flagging issue, but is there any documentation on how Immich is doing the PR site generation feature? That seems pretty cool, and I'd be curious to learn more.
Pretty sure Immich is on github, so I assume they have a workflow for it, but in case you're interested in this concept in general, gitlab has first-class support for this which I've been using for years: https://docs.gitlab.com/ci/review_apps/ . Very cool and handy stuff.