Just like apps and websites implement "Sign in with Apple" and Google couldn't we build some kind of federated authentication provider? Then everyone creates an account there and fedi apps can implement an easy way to authenticate users. Even non fedi apps could use it. I imagine user interaction between different fediverse platforms would be much easier too.

I guess could run an auth instance. Ideally everyone would run their own, keeping your data safe.

Is there something likes this already? Saw some discussion here but not much else https://socialhub.activitypub.rocks/t/single-sign-on-for-fediverse/712