Rerouted (regenerated, verified). Same repository and tag, but GitHub now builds the zip with different bytes, so it no longer matches the SHA-1 package.elm-lang.org recorded. The Lamdera package server serves a copy recovered from https://github.com/dillonkearns/elm-pages-v3-beta.
What we checked: Tag 8.0.0 is still on github.com/dillonkearns/elm-pages-v3-beta; its commit b7735572454e is from 2023-01-17 05:49 UTC, before the version was published (2023-01-17 05:52 UTC); elm.json is byte-identical to package.elm-lang.org's; the exposed modules match docs.json; the zip's SHA-1 is not the published one (GitHub's zip no longer comes out byte for byte the same), so the contents were checked instead.
The Lamdera compiler uses this copy and prints a one-line notice saying so. elm itself fails to download this version.
Details · package.elm-lang.org's zip: https://github.com/dillonkearns/elm-pages-v3-beta/zipball/8.0.0/
elm-pages manages the client-side state of fields, including Status which you can use to determine when in the user's workflow to show validation errors.