Jenna Smith with some pretty solid UX advice as it relates to loading states:
Rather than designing another loading state, I improve the preload strategy until the issue disappears entirely.
She points to Route Transitions and preloading data as solutions that get closer to pages that load everything at once, like a default website, while still keeping the SPA approach (assuming you actually need that).
Route transitions don’t eliminate loading, but they do give us a way to move it back to where I personally believe it belongs… at the app level rather than the component level.